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  • Vector Surveillance and Control
    LIAO Yuanhai, YE Jiahao, WU Caixia, LUO Zeyan, DENG Hui, HU Shengjun
    China Tropical Medicine. 2025, 25(11): 1456-1460. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.14

    Objective To determine the insecticide resistance levels of rural Aedes albopictus populations in Guangzhou, assess the impact of dengue vector control on insecticide resistance, and discuss the rational use of insecticides and resistance management strategies. Methods In July 2024, larval samples of Aedes albopictus were collected from four rural residential sampling sites within a 20-40 km radius of Guangzhou (with a distance of ≥20 km between each site). In the past three years, Dongxiang and Suishi villages had reported 18 and 3 cases of dengue fever, respectively; Xinhai and Donglong villages had reported none. The insecticide resistance levels of field-collected mosquitoes across all sampling sites were evaluated against beta-cypermethrin (conventional insecticide) along with propoxur and temephos (non-conventional insecticides). Insecticide resistance was determined by the larval immersion bioassays. Using the median lethal concentration (LC50) of a specific sampling site as the control, Probit regression analysis was conducted for each insecticide to determine whether inter-site differences in resistance were statistically significant. Results Using the LC50 of the sensitive population as the base, the test insects from Dongxiang village showed high resistance to beta-cypermethrin (116.85-fold), while those from Suishi and Donglong villages showed moderate resistance (21.41-fold and 12.63-fold, respectively); the test insects from Xinhai village showed moderate resistance to temephos (10.79-fold); all four populations demonstrated low-level resistance to propoxur, with resistance ratios ranging from 3.24 to 4.42. Using Xinhai as the reference population for beta-cypermethrin, resistance in Dongxiang and Suishi was significantly higher (P<0.05). In Dongxiang, resistance to temephos and propoxur was significantly lower than that to beta-cypermethrin (P<0.05). Conclusion In rural areas of Guangzhou where dengue outbreaks have been reported, Aedes albopictus exhibits high resistance to commonly used insecticides but lower resistance to less frequently used agents. In areas without dengue cases, resistance levels to all tested insecticides remain low. Local governments should scientifically use insecticides through environmental sanitation management, insecticide combinations, insecticide rotation, or the use of synergists to avoid or delay the development of resistance in Aedes albopictus during the handling of outbreaks.

  • Case Report
    NI Xiaofen, SHEN Lei, TENG Zhixiang, HU Haixia
    China Tropical Medicine. 2025, 25(11): 1507-1510. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.22

    Objective This report analyzes the investigation and emergency response to a case of imported chikungunya fever, along with the monitoring of mosquito vectors in the same period, to provide a reference basis for the prevention and control of chikungunya fever. Methods An epidemiological investigation was conducted in 2024 to study a case of chikungunya fever, including case search, emergency surveillance of mosquito vectors, and mosquito control measures. Pearson χ2 test was used to analyze mosquito surveillance data, including larval density in different habitats. Results Investigation revealed that the case had traveled to the Maldives with his wife from May 24 to June 1, 2024. After returning to Shanghai, he developed a fever on June 3. He visited Hospital A on June 4 and received treatments, including antipyretics and psychological counseling for stress relief, with no symptom improvement. On June 5, he presented to Hospital B, where an acute-phase serum sample was collected and sent to the CDC for nucleic acid testing for both dengue and chikungunya viruses. On June 7, the laboratory confirmed a positive result for chikungunya virus nucleic acid. The patient recovered following isolation and treatment, and no secondary cases were reported. Surveillance of Aedes vectors in July showed a Breteau index (BI) of 8.85 and a mosquito ovitrap index (MOI) of 7.19. A comparison of MOI in different habitats in 2024 revealed no statistically significant difference (χ2=5.45, P>0.05). ). Mosquito control and emergency surveillance were initiated on the day of diagnosis. After three consecutive days of mosquito control measures, the BI in the core area dropped rapidly from 10 to 3 by June 11, and the human-bait tent trap index dropped from an initial 4 mosquitoes/(trap·h) to 2 mosquitoes/(trap·h). Through sustained vector control measures, the BI and tent trap indices in the core area and precautionary area were maintained within safe limits throughout the outbreak period. Conclusion There is a risk of local transmission caused by imported chikungunya fever cases in Jing'an District, Shanghai. Early diagnosis and timely implementation of mosquito control measures are essential to prevent potential local epidemics.

  • Zoonotic Highly Pathogenic Infectious Diseases
    LI Libo, WENG Jian'e, GONG Xin, ZHANG Sheng, GUO Kelei, WEI Xinmei, FANG Liqun, WANG Guolin
    China Tropical Medicine. 2025, 25(8): 1022-1029. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.13

    As a "mixer" of influenza viruses, pigs can be infected by both human-origin and avian-origin influenza viruses, allowing for the easy generation of novel viral strains through gene reassortment. Currently, the Eurasian avian-like H1N1 (EA H1N1) virus has spread widely among pigs in Europe and Asia, and has caused human infections in many countries. In recent years, human infections with the EA H1N1 virus have been reported in many provinces in China, raising public health concerns. In pigs, EA H1N1 virus undergoes genetic recombination with other swine influenza viruses, resulting in numerous genetic variants. Among them, the G4 EA H1N1 virus has possessed the essential characteristics for human infection, enhanced pathogenicity and transmissibility in mammalian models. Serological investigations also reveal that swine-exposed population have higher seroprevalence against G4 EA H1N1 virus than that of general population, suggesting a greater risk of infection. This article provides a comprehensive review of origin and evolution of EA H1N1 virus, the pathogenicity and transmission of different EA H1N1 genotypes on mammalian models, impact of key amino acid site mutations, confirmed human infection cases, and serological investigations of human infection against EA H1N1 virus. It aims to offer reliable basis for control and prevention of EA H1N1 virus and to guide the future research direction.

  • Topic on Dengue Fever Epidemic and Control
    CHEN Qiulan, GUO Yu, ZHAI Hongrui, KANG Jiali, TANG Xun
    China Tropical Medicine. 2025, 25(9): 1155-1161. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.12

    Dengue fever imposes a growing global burden of disease, characterized by considerable spatiotemporal heterogeneity in its transmission dynamics. Epidemiological surveillance and early warning models serve as crucial tools for evaluating the risk of dengue outbreaks and transmission risks, thereby guiding subsequent targeted prevention and control efforts. This review synthesizes published studies on dengue surveillance and early warning models globally, examining their temporal and spatial distribution. It summarizes the predictive factors and modeling approaches employed in these models and evaluates the quality of the research. Meteorological and environmental variables, along with historical dengue surveillance data, are the most frequently utilized predictors. Modeling methodologies have evolved substantially, shifting from traditional time series analyses and infectious disease dynamic models to advanced machine learning techniques, with each method offering distinct advantages in various application scenarios. Future research should adhere to the reporting guidelines recommended by the recommended reporting items for epidemic forecasting and prediction research (EPIFORGE 2020) framework to improve study quality and practical value.

  • Topic on Dengue Fever Epidemic and Control
    HUANG Jingwen, LI Yuwei, CHEN Bin, ZHANG Canming, HUANG Zhiyu, LIAO Yanqing, WU Shenggen
    China Tropical Medicine. 2025, 25(9): 1131-1136. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.08

    Objective To monitor the density and seasonal fluctuation of dengue vector Aedes in Fujian Province from 2020 to 2024, and we provide scientific evidence for the prevention and control of dengue fever. Methods From March to November each year from 2020 to 2024, the double-layered tent method was used to monitor the density of adult Aedes, and Breteau index method was applied to monitor larval density. Statistical analysis of monitoring data were performed using Kruskal-Wallis H rank sum test, chi-square test, multivariate analysis of variance, and Spearman rank correlation analysis with SPSS 19.0 software. Results All Aedes mosquitoes captured were Aedes albopictus in Fujian Province from 2020 to 2024, none of Aedes aegypti were found. The average tent trapping index was 4.35 mosquitoes/(tent·hour); the average Breteau index (BI) was 6.96; the average container index (CI) was 14.12. Both the average tent trapping index and BI peaked in June. There were no significant differences between adult and larval densities across different years (P>0.05), with roughly the same trends annually. The highest average adult Aedes albopictus density [5.77 mosquitoes/(tent·hour)] was found in parks or bamboo forests, while the larval density was highest in residential areas and lowest in hospitals. Larva-positive water bodies were predominantly idle containers (bowls, bottles, jars and cans), accounting for 46.10%. There were at least 8 months each year when the densities of adult Aedes exceeded the dengue prevention threshold; and there were at least 6 months when the BI value exceeded the threshold. A strong positive correlation existed between tent trapping index and BI, with the regression equation: Y (tent trapping index)=0.748X(BI)-0.980. Conclusion The dengue vector Aedes are Aedes albopictus exclusively in Fujian Province, the activity of Aedes albopictus has been monitored from March to November; June to September represents the peak activity period, when it is necessary to pay more attention to the surveillance vector Aedes, controlling its density by eliminating larval-breeding sites, therefore to strengthen the ability of prevention and control of dengue fever.

  • Reviews
    ZHU Jialou, LI Peng, ZHAO Wenya, ZHANG Li, HU Jinxing
    China Tropical Medicine. 2025, 25(10): 1359-1406. https://doi.org/10.13604/j.cnki.46-1064/r.2025.10.21

    Tuberculosis (TB) is a major global public health challenge and remains the leading cause of mortality from a single infectious agent, posing a serious threat to the lives and health of people worldwide. The absence of an effective preventive vaccine and the rising prevalence of drug-resistant TB make early diagnosis and drug-resistance detection critical for the prevention and treatment of TB. Traditional testing methods are limited by insufficient sensitivity, long turnaround times, or narrow coverage of drug-resistance detection and therefore fail to meet clinical requirements adequately. In recent years, the field of high-throughput sequencing (HTS) has developed rapidly. This technology enables not only the rapid and highly sensitive identification of Mycobacterium tuberculosis but also the precise detection of multiple drug-resistant mutation sites, providing a novel set of tools to combat tuberculosis effectively. This review summarizes and evaluates the applications, advantages, and limitations of three high-throughput sequencing methods in the diagnosis of tuberculosis, including metagenomics next-generation sequencing (mNGS), targeted next-generation sequencing (tNGS), and whole genome sequencing (WGS), to provide a reference for the clinical implementation in tuberculosis diagnosis and drug resistance detection.

  • Articles
    LIU Meng, DONG Shuofan, BAI Guangyi, AN Ning, LI Yan, WANG Yingying, XU Xueang, ZHANG Yuqi, LU Xinli
    China Tropical Medicine. 2025, 25(9): 1206-1212. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.20

    Objective To understand the molecular transmission characteristics of newly reported HIV-1 infected individuals in Hebei Province from 2022 to 2023, analyze the transmission network, identify high-risk cases with a degree value ≥ 4, as well as the transmission of drug-resistant strains, so as to provide a reference for precise HIV intervention. Methods Plasma samples of newly reported HIV-1 infected individuals in Hebei Province from 2022 to 2023 were collected. The HIV-1 pol region gene was amplified through reverse transcription and nested polymerase chain reaction and drug resistance mutation analysis was used by the Stanford HIV Drug Resistance Database. The molecular transmission network was constructed using the TN93 model to analyze the high-risk transmission clusters. Logistic regression was used to analyze potential risk factors of the molecular transmission network (with the number of nodes ≥2). Arcgis analysis was carried out to display cross-city transmission intensity of HIV-1 infected individuals. Results Among the 555 HIV-1 infected individuals, the majority were male, Han ethnicity, and the transmission route was through homosexual. A total of 12 genotypes were identified. Among them, the main HIV-1 strains were CRF01_AE (46.7%) and CRF07_BC (38.7%). The drug resistance rate was 8.3%, and the most common drug resistance mutations were K103N (1.3%), followed by E138G (0.7%). Under the 1.5% gene threshold, a total of 182 sequences entered the molecular transmission network, forming 61 transmission clusters, with a network entry rate of 32.8%(182/555). The cases were mainly male (93.4%) and the transmission route was through homosexual (81.9%), It involved 11 cities and showed cross-regional transmission characteristics, and there were 13 cases with high transmission risk (degree ≥ 4 ). A total of 18 sequences carrying drug-resistant mutation sites were identified in 9 transmission clusters. Among them, the E138G drug-resistant mutation site was found to be spreading in a CRF07_BC transmission cluster (the number of nodes = 5). Multivariate logistic regression showed that clustering rate of student was higher than that of farmers (aOR=3.20, 95%CI:1.46-7.04); CRF01_AE (aOR=2.83, 95%CI:1.26-6.35) and CRF07_BC (aOR=3.60, 95%CI:1.60-8.12) had a higher clustering rate compared with the novel recombinant strains. In terms of regional transmission, the cross-city connections in the central and southern cities of Hebei Province were more frequent compared with northeastern cities. Conclusion We have identified high-risk populations and drug-resistant transmission clusters through the molecular transmission network. Strengthening precise intervention measures such as antiviral treatment and follow-up for high-risk populations is of great significance for controlling transmission of HIV and drug-resistant strains in Hebei Province.

  • Topic on Dengue Fever Epidemic and Control
    CHEN Jingjing, MENG Weiwei, LUO Huiming, WANG Rumin, LUO Yan, ZHANG Ling, JIN Yan, YIN Dapeng, CHEN Xuanshi, TAN Gaoling, QIU Li
    China Tropical Medicine. 2025, 25(9): 1124-1130. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.07

    Objective To compare the characteristics of dengue fever cluster epidemics in Hainan Province in 2023 and 2024, we provide evidence for comprehensive understanding of dengue fever epidemic patterns in Hainan Province and exploring more effective control and prevention measures. Methods Descriptive epidemiological methods were used to analyze the temporal, spatial, and demographic distribution, serological testing, case diagnosis, and clinical manifestations of dengue fever cluster epidemics in Hainan Province from 2023 to 2024. Excel 2021 and R 4.3.0 software were used for data processing and analysis, and ArcGIS 10.8 software was employed for visualization of geographical distribution. Results In 2023, 8 dengue fever cluster epidemics were reported, occurring from August to November, affecting 5 cities and counties, with 318 associated cases accounting for 87.60%(318/363) of the total reported cases that year. The main epidemic sites were communities and townships/rural areas, with dengue virus type 2 being the predominant strain (255, 80.70%). The M (P25, P75) interval from onset to diagnosis was 1(0.75, 2) days. In 2024, 9 dengue fever cluster epidemics were reported, occurring in July and October-November, affecting 4 cities and counties, with 62 associated cases accounting for 38.27% of the total reported cases that year. Communities/villages in cities were the primary epidemic settings, with dengue virus type 1 being the predominant strain (42, 67.74%). The M (P25, P75) interval from onset to diagnosis was 1(1, 3) days. No severe cases or deaths occurred among dengue fever cluster cases in both years. Statistically significant differences were observed in case source locations, occupation, virus serotype, and case detection methods (P<0.05), while no significant differences were found in gender, age, and interval from onset to diagnosis (P>0.05). Conclusion The scale of clustered epidemics in 2024 was significantly reduced compared to 2023, with cases detected timely. Future efforts should focus on continuously optimizing dengue fever control and prevention strategies, enhancing epidemic response capacity, and establishing more precise surveillance and early warning systems, with strengthened monitoring in coastal areas, tourist hotspots, and regions with frequent population movement during summer and autumn, expanding the scope of at-risk population screening, and improving surveillance sensitivity.

  • Articles
    LIU Xiaofang, LU Yanqiu, SUN Feng, WANG Jing, CHEN Yaokai
    China Tropical Medicine. 2025, 25(12): 1568-1571. https://doi.org/10.13604/j.cnki.46-1064/r.2025.12.09

    Objective To analyze the relationship between HIV-specific immune response in the plasma and viral reservoir size of individuals with human immunodeficiency virus (HIV) infection, and to explore new markers for evaluating HIV reservoirs. Methods A total of 96 HIV-infected individuals diagnosed at Chongqing Public Health Medical Center and followed up for at least 3 years from July 2021 to May 2024 were enrolled in this study. HIV DNA and cell-associated RNA (CA-HIV RNA) in peripheral blood mononuclear cells (PBMCs) were detected by fluorescence quantitative PCR, and HIV antibody levels in peripheral blood were quantitatively measured by immunosorbent assay. Combined with clinical infection parameters, correlation analysis was performed using the Spearman correlation coefficient. Results The median (interquartile range, IQR) age of the 96 participants was 51 (36, 59) years. Following long-term antiretroviral therapy (ART), the plasma viral load of all participants was suppressed to undetectable levels. The median M(P25, P75) levels of HIV DNA and CA-HIV RNA levels were 2.81 (2.29, 3.10)log10 copies / 106 PBMCs and 2.68(2.28, 2.98)log10 copies/106 PBMCs, respectively, and they were positively correlated (r=0.606 9, P<0.01). HIV DNA was positively correlated with baseline HIV RNA at 4.91 (4.40, 5.39) log10 copies/mL (r=0.3292, P<0.01). HIV DNA and CA-HIV RNA were both negatively correlated with baseline CD4+ cell counts of 177 (72, 287) cells/µL (r=-0.513 3, P<0.01; r=-0.322 8, P<0.01), while positively correlated with HIV p24 antibody levels of 2.61 (1.96, 3.08) light units (r=0.37, P<0.01; r=0.371 1, P<0.01), respectively. Conclusions In chronically HIV-infected individuals, pre-ART clinical parameters and post-ART specific antibody levels are closely associated with the size of the HIV reservoir. Therefore, monitoring these indicators could be valuable for assessing the viral reservoir in people living with HIV.

  • Articles
    LIU Shanhong, DONG Bing, ZHANG Wenqing, GUAN Na, XI Lin, BAI Xuejing, TA Na
    China Tropical Medicine. 2025, 25(10): 1245-1250. https://doi.org/10.13604/j.cnki.46-1064/r.2025.10.03

    Objective To analyze the epidemiological characteristics of brucellosis in Inner Mongolia Autonomous Region from 2019 to 2023, providing a reference for the prevention and control of human brucellosis. Methods A descriptive epidemiological method was employed to analyze the distribution patterns of human brucellosis and serum test results among high-risk populations in Inner Mongolia from 2019 to 2023. Meanwhile, brucellosis pathogens from the region were isolated, cultured, and identified by species and biotype during the same period. Results From 2019 to 2023, both the incidence rate and seropositivity rate of brucellosis in Inner Mongolia Autonomous Region showed an overall increasing trend. The annual incidence rates were 58.58/100 000, 68.28/100 000, 91.29/100 000, 79.49/100 000, and 70.58/100 000, respectively. A total of 732 230 serum samples from high-risk populations were tested, with 42 508 positive cases, yielding an average seropositivity rate of 5.81%. The annual seropositivity rates were as follows: 4.88% (6 034/123 746) in 2019, 4.80% (5 962/124 129) in 2020, 6.98% (10 042/143 791) in 2021, 6.41% (10 622/165 794) in 2022, and 5.63% (9 848/174 771) in 2023. Specifically, the rates exhibited an increasing trend from 2019 to 2021, peaking in 2021, followed by a declining trend from 2022 to 2023. Cases were reported across all 12 leagues/cities, with a cumulative total of 88 464 cases and an average annual incidence rate of 73.63/100 000. The seasonal indices for March to August were 121.05% (8 924/7 372), 135.70% (10 004/7 372), 139.93% (10 316/7 372), 148.54% (10 950/7 372), 145.59% (10 733/7 372), and 112.07% (8 262/7 372), all exceeding 100%, indicating an epidemic season during these months. Farmers constituted the majority of cases (78.60%, 69 532/88 464), the highest incidence was observed in the 40-60 age group (55.63%, 49 210/88 464), and the male-to-female ratio was 2.20:1 (60 856/27 608). Geographically, the epidemic showed a trend of spreading from east to west, with a stable incidence in the eastern region but a significant increase in the western region in recent years. During 2022-2023, 43 bacterial strains were isolated (17 in 2022 and 26 in 2023), all identified as Brucella melitensis, including 9 strains of biovar 1, 8 of biovar 2, 18 of biovar 3, and 8 atypical strains. Multilocus Sequence Typing (MLST) analysis revealed a predominance of sequence type 8 (ST8). Conclusion The brucellosis epidemic in Inner Mongolia remains severe, characterized by extensive geographic spread, high transmission intensity, and distinct seasonal patterns. It is recommended to enhance surveillance and prevention measures targeting high-risk populations, implement comprehensive control strategies to curb the epidemic further, and closely monitor the evolving trends of human brucellosis.

  • Articles
    LIU Rui, LIU Yao, FAN Mingqiu, LI Xin, LIU Hongxia
    China Tropical Medicine. 2025, 25(9): 1201-1205. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.19

    Objective To address the insufficient control efficacy against cockroaches in food service establishments caused by frequent chemical control of pesticide resistance, this study investigated the short-term rapid elimination and long-term sustained suppression effects of different combined insecticide strategies on cockroach populations, aiming to provide a scientific basis for optimizing integrated pest management (IPM) strategies. Methods Shanghai will be selected in August and September 2024 five eligible food service establishments were selected and divided into five experimental groups: Group 1 (Fipronil gel bait), Group 2 (Hydramethylnon gel bait), Group 3 (α-Cypermethrin spray + Fipronil spray), Group 4 (α-Cypermethrin spray + Fipronil gel bait), and Group 5 (Fipronil spray + Hydramethylnon gel bait). Gel baits were applied to hidden crevices according to product instructions, while spray insecticides were administered based on repellent or toxicant properties. Cockroach density was monitored using sticky traps before and after treatment, with density reduction rates calculated on days 1, 3, 7, 15, 30, and 45. Intergroup differences were analyzed using repeated-measures Friedman rank-sum tests‌.‌ Results Density reduction rates of‌ single gel bait groups (Groups 1 and 2) achieved 74.50% and 74.36% on day 7, reaching 88.56% and 89.74% on day 45, respectively. Density reduction rates of the dual-spray group (Group 3) showed 86.13% on day 7 and 98.02% on day 45. Combined groups (Groups 4 and 5) demonstrated reductions of 70.00% and 98.04% on day 7, and 88.46% and 99.51% on day 45, respectively. All five strategies achieved satisfactory control efficacy of cockroach(density reduction rates>80%). Group 5 (Fipronil spray + Hydramethylnon gel bait) outperformed the other four groups,with statistically significant differences(P<0.05). Conclusion Combined insecticide strategies, particularly spray-gel bait combinations, rapidly reduce cockroach density and sustain long-term suppression. The Fipronil spray and Hydramethylnon gel bait combination (Group 5) exhibited optimal comprehensive efficacy, and is recommended as a high-efficiency cockroach management protocol for food service establishments. Practical applications should flexibly select strategies based on infestation severity and environmental characteristics.

  • Research Report
    SUN Qintong, LIU Wenjie, WANG Ning, LI Wanfu, SUN Lin, HAN Yingnan, LIU Yan, CAO Xinyue, CAI Tong, WANG Xuejun
    China Tropical Medicine. 2025, 25(10): 1367-1370. https://doi.org/10.13604/j.cnki.46-1064/r.2025.10.22

    Objective To measure the effective protection time of several commonly used plant-derived crude extracts for mosquito repellency against Aedes albopictus, and evaluate their repellent effects on Aedes albopictus, so as to provide a basis for the research and development of plant-derived mosquito repellents. Methods Peppermint (Mentha haplocalyx Briq.), duckweed (Spirodela polyrhiza (L.) Schleid.), grassleaf sweetflag rhizome (Acorus tatarinowii Schott), and rosemary (Rosmarinus officinalis L.) were crushed and extracted with absolute ethanol. The repellent effects against Aedes albopictus were assessed using the method outlined in "Laboratory Efficacy Test and Evaluation of Hygienic Insecticides for Pesticide Registration Part 9: Repellents" (GB/ T13917.9-2009). One-way analysis of variance (ANOVA) was used to analyze differences in mosquito repellency duration among different solutions, while repeated-measures two-factor multi-level ANOVA was used to test whether differences existed in repellency duration against Aedes albopictus across various concentrations of the solutions. Results Under laboratory conditions, the average number of landing test mosquitoes across the six groups was (33.92±5.49), and the attack power test was qualified. The average repellency durations for rosemary, grassleaf sweetflag rhizome, and peppermint at all four dilution concentrations were longer than those in the control group. There were statistically significant differences in mosquito repellency durations between different dilution concentrations of peppermint, duckweed, grassleaf sweetflag rhizome, and the compound formulation (F=8.63, 3.32, 12.53, 10.29, all P<0.05). The average repellency duration of peppermint, grassleaf sweetflag rhizome, and rosemary at concentrations of 15% and 20% all exceeded 4 h; the average repellency duration for grassleaf sweetflag rhizome at 10% concentration was 4 h; whereas the average repellency duration for all four types of plant-derived crude extracts at 5% concentration was less than 4 h. With the decrease of concentration, the mosquito repellency durations for peppermint, duckweed, grassleaf sweetflag rhizome, and the compound formulation showed a general shortening trend. Conclusion Peppermint, grassleaf sweetflag rhizome, and rosemary exhibit certain repellent effects against Aedes albopictus. Higher concentrations of plant-derived mosquito repellent solution demonstrate superior repellency and warrant further development and application.

  • Articles
    WU Ping, ZHUANG Li, ZHENG Ju, KE Qian
    China Tropical Medicine. 2026, 26(1): 80-87. https://doi.org/10.13604/j.cnki.46-1064/r.2025-1454

    Objective To analyze the epidemic characteristics and hemagglutinin (HA) gene variations of influenza B virus (IBV) in Guizhou Province from 2022 to 2024, aiming to provide a basis for optimizing the local influenza prevention and control strategies. Methods A total of 76 976 samples were collected from patients with influenza-like illness (ILI) at 13 sentinel hospitals for influenza surveillance in Guizhou Province from January 2022 to December 2024. Influenza B virus nucleic acid was confirmed by real-time fluorescence quantitative polymerase chain reaction (qPCR), and virus isolation was performed using MDCK cells. Fifty-two isolates of influenza B virus were selected for sequencing. Phylogenetic trees were constructed using bioinformatics software, and their molecular evolutionary characteristics were analyzed. Results A total of 2 893 cases of influenza B were detected, with a detection rate of 3.76% (2 893/76 976), all of which belonged to the Victoria subtype. The detection rate varied significantly by year (P<0.001), peaking in 2022 (6.75%), and also by age group and season (P<0.001 for both). There was no significant difference between genders (P=0.222). The highest detection rates were observed in the 15-<60 age group (5.38%) and during winter (10.21%), followed by spring (4.51%). Phylogenetic analysis showed that the HA gene sequences of all 52 isolates were highly homologous and clustered within the V1A.3 subclade, alongside the B/Austria/1359417/2021 vaccine strain. Eight amino acid mutations occurred in the key antigenic epitope regions (120-loop, 150-loop, 190-helix) of the HA protein. Forty-nine of the isolates shared 10 conserved potential N-glycosylation sites with the vaccine strain. Conclusion Influenza B in Guizhou Province shows a winter-spring epidemic pattern, with young and middle-aged adults as the key population for prevention and control. The V1A.3 clade of the B/Victoria subtype is the predominant strain. While the HA gene of circulating viruses showed good homology to the contemporary vaccine strain, the presence of site mutations in key antigenic determinant regions highlights the need for dynamic monitoring and timely update of vaccine components.

  • Topic on Dengue Fever Epidemic and Control
    LIN Jiawei, HUANG Fulin, WU Shenggen, XIE Zhonghang, HUANG Wenlong, YE Wenjing, OU Jianming, CHEN Wu, MAO Yimeng
    China Tropical Medicine. 2025, 25(9): 1119-1123. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.06

    Objective To analyze the epidemiological characteristics of imported dengue fever in Fujian Province, aiming to provide a reference for accurate and scientific prevention and control of dengue fever. Methods Surveillance data on imported dengue fever cases reported in Fujian Province from 2005 to 2023 were collected through the Chinese Center for Disease Control and Prevention Information System. Descriptive epidemiological methods were employed to analyze the distribution characteristics of imported dengue fever. Heat maps, Sankey diagrams, and regression curves were generated using R software. Results From 2005 to 2023, a total of 1 186 imported dengue fever cases were reported in Fujian Province from 2005 to 2023, exhibiting an overall upward trend (except for 2020-2022). The trend in the number of affected counties (cities, districts) was consistent with the trend in the number of reported cases. The distribution of cases displayed a significant seasonal pattern, with peaks occurring annually from June to October. Imported cases were reported in 62 counties (cities, districts) across 9 prefecture-level cities and the Pingtan Comprehensive Experimental Zone, with Quanzhou (423 cases, 35.67%), Fuzhou (316 cases, 26.64%), and Xiamen (221 cases, 18.63%) accounting for 80.94% (960/1 186) of the total imported cases. Imported dengue fever cases in Fujian Province originated from 31 countries and regions worldwide, with the Western Pacific Region being the most common source (933/1 186, 78.67%). The main countries of origin were Cambodia (550 cases, 46.37%) and the Philippines (263 cases, 22.18%). Among imported cases, the gender ratio (male: female) was 3.18:1 (902/284); the majority of patients (91.23%, 1 082/1 186) were aged 21-60 years; the top three occupations among cases were homemakers/unemployed, farmers, and commercial services, collectively accounting for 63.83% (757/1 186) of all imported cases. The median from symptom onset to diagnosis was 5.3 days, showing an overall downward trend. A linear relationship was found between the number of imported cases and the number of inbound international travelers, described by the equation y=0.021 7x+0.374 3 (R2=77.78%, F=59.51, P<0.001). Conclusion The epidemic of imported dengue fever in Fujian Province shows a sustained upward trend, with distinct temporal, spatial, and demographic clustering of cases. Therefore, it is recommended to enhance the prevention and control of dengue fever among key inbound populations, tailored to specific temporal and geographical risk factors.

  • Zoonotic Highly Pathogenic Infectious Diseases
    TIAN Feng, XIAHOU Weimin, MA Xuezheng, LU Yaoqin, ZHOU Linfu, YIN Xiaoping
    China Tropical Medicine. 2025, 25(8): 958-964. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.03

    Objective To understand the pathogen carried by small mammals in the border port areas between China and Kazakhstan, as well as China and Mongolia, and the transmission mechanism and route of their natural foci, so as to provide a basis for controlling the spread of zoonoses. Methods From 2019 to 2023, small animals were captured using the rat trap method and the night trap method. Their species were identified by morphology, and the tissues inside the animals were collected. The pathogens and vectors carried by the animals were detected by serological and molecular biological methods, and the transmission modes were analyzed. Results A total of 1 619 small mammals, belonging to 5 orders, 13 families, 30 genera and 40 species, were collected. Among 354 long-tailed yellow rats collected from the Hongshanzui Port on the China-Mongolia border, 22 positive samples of 5 pathogens were detected, with a positive rate of 6.21% (22/354). Among 191 samples collected from the Takshken and Hongshanzui port areas on the China-Mongolia border, 39 positive samples of 4 myiasis pathogens were detected in 4 hosts, with a positive rate of 20.42% (39/191). Among 192 samples collected from three hosts in the border areas of Takshken and Jimunai, 60 positive samples of two intestinal parasitic disease pathogens were detected, with a positive rate of 31.25% (60/192). A total of 1 719 samples of 15 hosts were collected from 7 major border port areas. Among them, 201 positive samples of 17 pathogens were detected, with a total positive rate of 11.69% (201/1 719). Conclusion Among the dominant species of small mammals distributed in the border port areas of China, Kazakhstan and Mongolia in Xinjiang, 17 kinds of natural foci pathogens are carried. Diseases are transmitted through various infection vectors and various diffusion methods. It is necessary to strengthen the publicity and education of prevention and control knowledge for the local people and further carry out disease monitoring in this area. It provides important basis and clues for the prevention and control of major and emerging zoonotic diseases such as plague in border areas.

  • Vector Surveillance and Control
    LIU Yan, ZHAO Zhigang, HAN Yingnan, CAO Xinyue, SUN Qintong, CAI Tong, LIU Wenjie, WANG Xuejun
    China Tropical Medicine. 2025, 25(11): 1371-1375. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.01

    Objective To analyze the species composition, density distribution, seasonal fluctuation, and insecticide resistance of flies, particularly Musca domestica, in Shandong Province, China, thereby providing a scientific basis for the prevention and control of flies. Methods The cage trapping method was used for fly ecological surveillance, and the topical application method was employed to determine the insecticide resistance of M. domestica. Excel 2010 and SPSS 20.0 software were used to analyze the surveillance data statistically. The chi-square test was used to compare the composition of fly species. Fly densities were compared by the one-way ANOVA or the Kruskal-Wallis H test. The Probit regression model was used to calculate the median lethal dose (LD50), 95% confidence interval (CI), and virulence regression equation. Results From 2019 to 2023, a total of 10 371 fly traps were deployed in Shandong Province, capturing 68 668 flies, with an overall average density of 6.62 flies/cage. The dominant species were M. domestica, Sarcophagidae, M. sorbens, and Lucilia sericata, accounting for 57.31%, 10.35%, 8.26%, and 7.57% of the total catch, respectively. Among the four types of habitats, the density of flies in farmers' markets was highest, reaching 9.59 flies/cage, followed by green belts, catering surroundings, and residential areas, showing significant differences in fly density among different habitats (H=11.777, P<0.01). Fly density showed a unimodal pattern, with peak periods occurring from June to August. All habitats also displayed a unimodal pattern, with peaks occurring from June to July. M. domestica showed resistance to beta-cypermethrin, lambda-cyhalothrin, deltamethrin, permethrin, propoxur, temephos, but remained sensitive to tetramethrin, dichlorvos, malathion, and imidacloprid. Conclusions Shandong Province exhibits a diverse fly population, with dominant species, such as Musca domestica and Sarcophagidae, requiring targeted control efforts. Fly density peaks from June to August, and farmers' markets are key places for targeted fly control. Therefore, it is recommended that integrated control measures be implemented in key locations prior to peak fly activity periods to reduce fly density. M. domestica has developed varying levels of resistance to certain insecticides. Future control efforts should involve the scientific and rational use of insecticides to delay the emergence of resistance.

  • Zoonotic Highly Pathogenic Infectious Diseases
    ZHAO Kefu, JIANG Chunxiao, HU Yuqian, TANG Renshu, YU Junling, ZHANG Wenyan, LIU Xuxiang
    China Tropical Medicine. 2025, 25(8): 1016-1021. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.12

    Objective To analyze clinical and epidemiological characteristics of the first human case of H5N6 avian influenza in Hefei City, and to provide a scientific basis for control and prevention of similar animal-origin influenza outbreaks in humans. Methods Field epidemiological investigation methods were used to collect and analyze basic information of the case, course of illness and medical consultation, history of poultry exposure, tracking and screening of close contacts, and testing results of relevant specimens. Results The case was an elderly female who presented with flu-like symptoms in the early stages of illness. The condition progressed rapidly, with time intervals from onset to first consultation, hospitalization, conversion to severe condition, use of anti-influenza drugs, laboratory confirmation, and death being 1 day, 2 days, 2 days, 4 days, 7 days, and 22 days, respectively. The patient had a clear history of exposure to live poultry (chickens), and the positive rate of H5N6 virus in the supply market environment was 20.00%. The results of gene sequencing showed that, the HA gene segment belongs to the same lineage as H5N6 strains isolated from chickens and crows in Japan in 2022 and 2023, and the H5N6 strain isolated from cats in South Korea in 2023; while the NA gene segment belongs to the same lineage as H5N6 strains isolated from mandarin ducks in South Korea in 2023 and from wild birds in Zhejiang, China in 2024. Expanded surveillance revealed that the positive rate of H5N6 in environmental samples from markets with live poultry sales was significantly higher than that in markets without live poultry sales (60.00% vs. 1.27%, χ⊃2;=88.364, P<0.001). No secondary cases were found among the 44 close contacts and co-exposed individuals. Conclusion This is the first human case of H5N6 avian influenza in Hefei City, with the source of infection being exposure to live poultry. The sale of live poultry is a risk factor for human infection with H5N6 avian influenza. It is recommended to prohibit the trade of live poultry in urban areas and even the entire city, promote centralized slaughter, cold chain transportation, and fresh poultry sales policies, strengthen public health education, encourage citizens to purchase and consume "qualified poultry", and reduce direct contact with live poultry to lower the risk of infection.

  • Articles
    XU Pingping, ZONG Shuai, XU Yinhai, KANG Haiquan, DING Xinglong
    China Tropical Medicine. 2025, 25(11): 1486-1492. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.19

    Objective To retrospectively review the data of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections, investigate their clinical distribution and drug resistance, and detect Staphylococcal Cassette Chromosome mec (SCCmec) and pvl genes in the isolates. This study aims to characterize the epidemiological features of MRSA, predict its trends, and provide a reference for infection control and clinical therapeutic strategies. Methods MRSA data from 2020 to 2024 were extracted from the Laboratory Information System (LIS) and WHONET databases of three Grade III-A general hospitals. Non-redundant isolates from clinical specimens of hospitalized patients with antimicrobial susceptibility records were included. Detection rates, drug resistance rates, specimen sources, and high-risk departments were analyzed. A random selection of 129 cryopreserved MRSA isolates underwent PCR amplification for mecA, SCCmec types Ⅰ-Ⅴ, and pvl genes. Results A total of 3 065 eligible MRSA isolates were identified across the three hospitals. The annual MRSA detection rates over five years ranged from 49.7% to 56.2%, with significant inter-hospital differences (all P<0.01); hospital B exhibited the highest rate (57.3%-63.6%). MRSA demonstrated 100.0% susceptibility to linezolid, vancomycin, and teicoplanin, and low-level resistance to rifampicin and chloramphenicol. Isolates were mainly derived from sputum (50.8%), blood (14.6%), and secretions (13.9%). ICU contributed 47.4% of MRSA isolates. Among the 129 tested strains, mecA carriage was observed in 98.5% (127/129). The predominant SCCmec types wereⅢ (47.3%, 61/129) and Ⅱ (40.3%, 52/129), with type Ⅳb detected in 7.8% (10/129) of the samples. The pvl gene positivity rate was 7.0% (9/129). Conclusion Over the five-year period, MRSA detection rates in three hospitals were notably higher than national averages for the same period, albeit with a slow downward trend. The MRSA isolates exhibited multidrug resistance to various antimicrobial agents, although no strains resistant to vancomycin or linezolid were found.

  • Topic on Dengue Fever Epidemic and Control
    HUANG Zhenzhi, ZHOU Lu, QIN Fei, CHENG Jinzhi, XIAO Qiuqiu, WU Jiahong, SHANG Zhengling
    China Tropical Medicine. 2025, 25(9): 1087-1093. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.01

    Objective To investigate the effect of Aedes albopictus mosquito saliva protein (al-MSP) on the infection of human cerebral microvascular endothelial cells (hCMEC/D3) by Dengue virus type 2 (DENV-2). Methods Saliva of adult female Aedes albopictus was collected by sugar-water feeding method, concentrated by ultrafiltration, and then mosquito salivary protein (al-MSP) content in saliva was quantified by BCA protein quantification method. The blood-brain barrier (BBB) model was simulated by inoculating hCMEC/D3 cells in a Transwell. The hCMEC/D3 cells were treated with al-MSP, DENV-2 and al-MSP+DENV-2, Evans blue-serum albumin (EB-BSA) permeation assay was used to assess hCMEC/D3 cell barrier permeability; expression of intracellular intercellular tight junction proteins ZO-1, Occludin, Claudin-5 and DENV2-E mRNA were detected by qRT-PCR; expression of ZO-1, Occludin, Claudin-5, and DENV2-E protein were detected by immunoblotting and immunofluorescence. Results At MOI of 0.1 and 0.5 DENV-2 infected cells for 24 h, EB-BSA concentrations in the lower chamber of BBB model were 32 μg/mL and 68 μg/mL, respectively, indicated that DENV-2 infection significantly increased permeability of the endothelial barrier of hCMEC/D3 cells, whereas treatment with al-MSP alone did not alter the permeability. al-MSP of 0.2, 2 μg/mL increased DENV-2 (MOI=0.1) infected hCMEC/D3 permeability by 38% and 47%, respectively. DENV-2 down-regulated relative mRNA expression of hCMEC/D3 intercellular tight junction proteins ZO-1, Occludin, Claudin-5. ZO-1, Occludin, Claudin-5 mRNA expression in infected cells under the effect of 0.2 μg/mL al-MSP was significantly down-regulated compared to the effect of the virus alone (P<0.001); ZO-1, Occludin (P<0.05) protein expression were all decreased, and Claudin-5 also showed some decreasing trend (P>0.05); ZO-1 protein immunofluorescence intensity was decreased, but the relative expression of DENV-2 E gene mRNA was increased by 2.4-fold (P<0.001), and the expression of DENV2-E protein was also increased (P<0.001). Conclusions Aedes albopictus salivary proteins promotes DENV-2 disruption of the endothelial barrier in hCMEC/D3 cells, which may be associated with its enhanced DENV-2 replication.

  • Topic on Dengue Fever Epidemic and Control
    CHEN Chuding, WU Yang, GUAN Xuhua, HUANG Danqin, ZHANG Weiming, LIU Man, FANG Can, REN Yuxing
    China Tropical Medicine. 2025, 25(9): 1094-1099. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.02

    Objective To analyze the epidemiological characteristics of dengue fever (DF) cases reported in Hubei Province from 2015 to 2024, providing a reference for optimizing regional DF prevention and control strategies. Methods Descriptive epidemiology and spatial autocorrelation were used to analyze DF case surveillance data from 2015 to 2024 in Hubei Province, sourced from the China CDC Information System. Results From 2015 to 2024, a total of 557 DF cases were reported in Hubei Province, including 505 imported cases (90.67%). The main sources of importation were Cambodia and Guangdong. The male-to-female ratio was 2.59∶1, with 68.76% of cases occurring in young and middle-aged adults aged 30-59 years, and 44.70% being farmers or migrant workers. The peak incidence period was July to November. Based on the incidence status, DF epidemics in Hubei Province can be divided into four phases: 2015-2018, 2019, 2020-2022, and 2023-2024. Local cases were reported in 2019, 2023, and 2024. Epidemiological characteristics differed significantly across these phases, mainly in terms of age, occupation, case type, time interval from onset to diagnosis, and importation source (all P<0.05). Except for the Shennongjia Forestry District, reported cases have affected 86 counties and districts across 16 prefecture-level cities in Hubei Province, while local cases affected 11 counties in 5 cities, with the scope continuing to expand. Cases in 2019 and 2024 exhibited spatial clustering patterns (global Moran's I>0, indicating positive correlation; P<0.05). Local spatial autocorrelation analysis identified that the border areas among four cities—Wuhan, Ezhou, Huanggang, and Huangshi—as hotspots for both imported and local cases, making them key regions for DF prevention and control in Hubei Province. Conclusion From 2015 to 2024, DF in Hubei Province was predominantly caused by imported cases, with varying epidemiological characteristics across different periods. The disease exhibited spatial clustering, and its geographic scope continued to expand. Enhanced prevention and control measures should be implemented during high-incidence seasons, targeting key areas and populations.

  • Zoonotic Highly Pathogenic Infectious Diseases
    XIAO Shan, LI Lingzhi, HUANG Zheng, OU Xinhua, YAO Dong, PEI Ruiqing
    China Tropical Medicine. 2025, 25(8): 1004-1011. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.10

    Objective To analyze molecular tracing and evolutionary characteristics of H9N2 avian influenza virus (AIV) strains isolated from two human cases and related environmental samples collected from live poultry markets (LPMs) in Changsha City in April 2025, provide scientific basis for avian influenza prevention and control. Methods Gene sequencing was performed on H9N2 AIVs obtained from throat swabs of the two cases and environmental samples. Genetic evolution analysis on HA and NA genes, homology, receptor-binding specificity, protein activity, drug resistance, and N-glycosylation patterns were focused. Results A total of 10 H9N2 avian influenza virus (AIV) gene sequences were obtained, including 1 whole genome. Homology analysis revealed that the HA gene was most similar to strains isolated from Fujian Province, while the NA gene was most similar to isolates from Fujian and Chongqing. HA gene belonged to the Y280-like h9.4.2.5 lineage, featuring a cleavage site of PSRSSR↓GLF. The receptor-binding site harbored Q226L and Q227M substitutions, and multiple antigenic mutations were observed compared to Y280-like vaccine strains. N-glycosylation site prediction identified 7 potential sites in all strains. All NA gene exhibited a deletion at amino acid positions 55-57 in the stalk region. Key active-site mutations (K135E, I145T) were mutanted, along with one or more substitutions in head epitopes, but no antiviral resistance markers were found. N-glycosylation analysis revealed 4 potential sites in 9 strains and 3 in 1 strain, the latter possibly linked to an N78D substitution upon sequence alignment. Conclusion The H9N2 avian influenza virus exhibited diverse mutations in key sites and functional domains detected in Changsha in April 2025, with multiple transmission chains spreading locally. Multifaceted measures should be strengthened to enhance epidemic control and prevention.

  • Articles
    Paziliya Aini, Yipaer Aiheiti, ZHAO Yuhua, Muhebuli Nuermaimaiti, WANG Rui, Gulijiamali Rexiding, LIU Nianqiang
    China Tropical Medicine. 2025, 25(12): 1533-1539. https://doi.org/10.13604/j.cnki.46-1064/r.2025.12.04

    Objective To describe and analyze the epidemiological characteristics of Xinjiang Uygur Autonomous Region from 2005 to 2023, and to provide evidence-based support for scientific decision-making regarding tuberculosis (TB) prevention and control in Xinjiang. Methods Data on reported pulmonary tuberculosis cases from 2005 to 2023 were obtained from the National Infectious Disease Reporting System. The study analyzed the spatiotemporal trends of TB incidence in Xinjiang as a whole and in its southern and northeastern regions, etiological characteristics, and demographic distribution (gender, age, and occupation) of the cases. Results From 2005 to 2023, Xinjiang reported a total of 750 103 cases of pulmonary tuberculosis (including tuberculous pleurisy), with the number of reported cases showing an initial rise followed by a decrease. In 2023, the etiological positivity rate of reported tuberculosis patients in Xinjiang was 58.50%, which represents an increase of 31.37% compared to the 44.54% reported in 2005. The incidence rate generally declined from 2005 to 2015 [annual percent change (APC)=-1.97%], rose significantly from 2015 to 2018 (APC=18.20%), dropped markedly from 2018 to 2021 (APC=-35.45%), and experienced a slight rebound from 2021 to 2023 (APC=7.36%). In the five prefectures of southern Xinjiang, incidence increased from 2005 to 2018 (APC=3.76%) and fell from 2018 to 2023 (APC=-24.10%), while northeastern Xinjiang experienced a continuous decline throughout the same period (APC=-5.15%). More males were affected than females (Male-to-female ratio=1.17∶1). The proportion of cases among children <15 years old decreased (APC=-5.29%), while the proportion among elderly individuals ≥65 years old increased (APC=1.99%). Farmers, herdsmen, and fishermen constituted the primary affected group, accounting for 69.93% of cases. Conclusion From 2005 to 2023, the reported TB incidence rate in Xinjiang exhibited a fluctuating downward trend. Notably, after implementing the "Xinjiang Model" TB incidence in Xinjiang significantly decreased, demonstrating substantial progress in TB control. Moving forward, it is essential to implement region-specific and category-based strategies to ensure the high-quality and sustainable advancement of the "Xinjiang Model", there by accelerating progress toward ending the TB epidemic.

  • Articles
    LI Fuyu, WANG Jiajun, LENG Jun, LI Liuxing, HUANG Jie, ZHANG Junmei, ZHOU Yan, LI Zhang, YU Jun, ZHENG Yaxiong, YU Qian, WANG Jiali, WANG Jinglin
    China Tropical Medicine. 2025, 25(9): 1174-1180. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.15

    Objective To understand the molecular characteristics of Coxsackievirus A16 (CVA16) in the border area of Xishuangbanna, Yunnan Province, and the evolutionary relationship between the epidemic strains at home and abroad, so as to provide a scientific basis for control and prevention, and its molecular traceability of CVA16 in Xishuangbanna. Methods In December 2024, throat swabs from children diagnosed clinically as suspected hand-foot-mouth disease were collected in the First People's Hospital of Jinghong City, Xishuangbanna Prefecture. Viral nucleic acids were extracted, Nested RT-PCR was used to amplify VP1 gene sequence of the virus. Sequence analysis was conducted using bioinformatics software such as MEGA 7.0. Results A total of 36 throat swab samples of suspected HFMD children were collected; 3 samples were positive for CVA16-VP1 (sample number: 3/JH-YN/2025, 5/JH-YN/2025, 6/JH YN/2025VP1), and the detection rate was CVA16 (8.33%). The results of sequence analysis showed that the three sequences obtained in this study were located in the same evolutionary branch with the epidemic B1a gene subtype CVA16 in Jiangxi Province of China in 2022 and 2023, with nucleotide homology of more than 89% and amino acid homology of more than 92%; while other subtypes of CVA16 were located in different evolutionary branches, with nucleotide homology less than 89% and amino acid homology less than 90%, suggesting that CVA16 B1a was the main subtype of HFMD virus in Jinghong in December; Amino acid analysis showed that the three positive strains in Jinghong city were in line with the current epidemic pattern of the novel B1a gene VP1-164K/251I, and there were 4 mutations in 16 mutation-prone sites. The 145th amino acids were not mutated, which was consistent with E145V, that is, the virulence of local epidemic strains might be enhanced. There were site-specific mutations of individual strains in 252, 261 positions, and 266 site-specific mutations in all three strains, which might be related to adaptive transmission or specific mutations produced by local strains to enhance epidemic of the virus in the population. Conclusions In December 2024, there was a CVA16-B1a subtype epidemic in Jinghong, Xishuangbanna, which was closely related to the epidemic strains in other areas of Yunnan and Jiangxi in recent years, providing a scientific basis and guiding significance for the diagnosis and prevention of HFMD in this area.

  • Zoonotic Highly Pathogenic Infectious Diseases
    MAO Chunpeng, ZHANG Yan, WANG Xinqi, LONG Ying, ZHOU Jianghua, BAI Zhechun, LI Fan, ZHONG Youhong, WANG Peng
    China Tropical Medicine. 2025, 25(8): 990-996. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.08

    Objective To analyze the biological characteristics and genomic features of Yersinia enterocolitica phage vB_Yen_YN202-142, and to provide references for prevention and treatment of Yersinia enterocolitica. Methods Using Y. enterocolitica as the host strain, phages were isolated from the cecum of Apodemus chevrieri. Morphology was observed by transmission electron microscopy (TEM), and stability, optimal multiplicity of infection (MOI), one-step growth curve, and host range were determined. Open reading frames (ORFs), phylogenetic tree construction and comparative genomic analysis were predicted through whole-genome sequencing. Results A novel Y. enterocolitica phage, vB_Yen_YN202-142, was isolated. It formed transparent plaques (2.0-3.0 mm in diameter) surrounded by a 0.5 mm semi-transparent halo. TEM revealed a head and a contractile tail. The phage titer decreased significantly after 30 min of UV exposure and was inactivated by 75% ethanol within 1 h. It remained stable at 4-60 ℃ and pH 5.0-9.0, with an optimal MOI of 0.1, a latent period of 3 min, and a burst size of 83 PFU/cell. It showed lysis activity against multiple strains of Yersinia enterocolitica and Yersinia pestis of different serotypes. The genome was 51 163 bp, GC content: 46.93%, encoding 94 ORFs classified into five functional groups: structural proteins, DNA packaging, DNA metabolism/replication, host lysis, and hypothetical proteins. Conclusion A bacteriophage vB_Yen_YN202-142, isolated from cecum of an adult male A. chevrieri in a plague foci, represents a new member of Caudoviricetes. Its short latent period, robust stability, and broad lytic activity enrich the Y. enterocolitica phage repository and provide a scientific basis for phage therapy against yersiniosis and the control of Y. enterocolitica.

  • Topic on Dengue Fever Epidemic and Control
    CAO Yiou, YUAN Heng, ZHOU Xingyu, LIU Yaqiong, XIAO Chongkun
    China Tropical Medicine. 2025, 25(9): 1108-1112. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.04

    Objective To analyze the epidemiological characteristics of dengue fever cases in Sichuan Province from 2019 to 2024, and to provide a scientific basis for formulating dengue fever prevention and control measures. Methods Data on dengue fever cases in Sichuan Province from 2019 to 2024 were collected from the China Information System for Disease Control and Prevention. Descriptive epidemiological methods were employed for the analysis of epidemic characteristics. Results A total of 641 cases of dengue fever were reported in Sichuan Province from 2019 to 2024, including 611 imported and 30 local cases. Dengue fever cases were reported throughout the year, with peaks in summer and autumn. Local cases occurred exclusively from August to October, with the highest incidence in September (83.33%). Cases were reported in 119 districts/counties across 20 cities/prefectures in the province, with the top five being Chengdu, Luzhou, Deyang, Yibin, and Nanchong. Cities/prefectures with higher reported case numbers were concentrated in Chengdu and the eastern and southern regions of Sichuan. Local cases were reported in Luzhou, Guang'an, Dazhou, and Chengdu. The sex ratio of male to female cases was 1.68:1. Cases were concentrated in the 20 to <60 age group (89.24%), with an age [M (P25, P75)] of 35(28.0, 47.0) years. The top three occupations were farmers/migrant workers/workers (231 cases, 36.04%), housework and unemployment (146 cases, 22.78%), and business services (77 cases, 12.01%). Statistically significant differences were observed in occupational composition across years (χ2=43.157, P<0.01), as well as in sex ratios (χ2=5.056, P<0.05) and occupation (χ2=15.37, P<0.01) between local and imported cases. Overseas imported cases accounted for 64.65% (395/611), mainly from Southeast Asia (93.16%, 368/395), with Cambodia being the most common source. Domestic imported cases accounted for 35.35% (216/611), mainly from Yunnan Province and Guangdong Province. The median interval from onset to diagnosis was 6.4(3.7,9.0) days. A statistically significant difference was found in the onset-to-diagnosis interval across years (χ2=30.669, P<0.01). Conclusions From 2019 to 2024, the number of dengue fever cases in Sichuan Province remained at historically high levels, with sporadic local outbreaks. During peak seasons, it is recommended to strengthen joint prevention and control efforts, strengthen monitoring, standardize epidemic disposal, implement prevention and control measures, and provide targeted health education to high-risk populations.

  • Articles
    HUANG Shourui, CHEN Yongchang, WEI Xiaoling, LIU Hui, XUE Min, JIANG huiyu, LIU Miao, WANG Bing, LIU Yanqin, MA Xiang
    China Tropical Medicine. 2025, 25(11): 1461-1466. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.15

    Objective To understand the changes in antigen genotypes of clinical isolates of Bordetella pertussis (Bp) in Shandong province from 2014 to 2022, aiming to provide a reference for the optimization of pertussis vaccines. Methods Bp strains were clinically isolated from patients at the Children's Hospital Affiliated to Shandong University between 2014 and 2022. The major antigen genes ptxA, ptxC, ptxP, prn, fim2, fim3, and tcfA of Bp isolates were amplified by PCR to determine their antigen genotypes. Genotype distributions were compared across time periods, differences between vaccinated and unvaccinated infection groups were assessed, and findings were compared with the antigen genotypes of vaccine strains currently used in China. Results Six antigen genotype profiles were identified among Bp isolates in Shandong Province during 2014-2022, of which the most prevalent antigen genotype was ptxA1/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2 (73.27%), followed by ptxA1/ptxC4/ptxP3/prn150/fim2-1/fim3-1/tcfA2 (22.78%). The prevalence of genotypes ptxC1, ptxP1, and prn1 was highest in 2014-2016, followed by 2020-2022, and lowest in 2017-2019; however, these temporal differences were not statistically significant (P>0.05). In contrast, ptxC4, ptxP3, and prn150 were not detected before 2020 and only appeared in the 2020-2022 period, a statistically significant emergence (P<0.001). Among the isolates from 2020-2022, no significant difference in prevalence was observed between ptxC1 and ptxC4, ptxP1 and ptxP3, or prn1 and prn150 (P>0.05). The differences in antigen genotypes between the vaccinated and unvaccinated groups were not statistically significant (P>0.05). Finally, compared with the vaccine strain, the major change of Bp epidemic strains in Shandong Province was the substitution of ptxA1 for ptxA2. Conclusions From 2014 to 2022, the predominant antigen genotype among circulating Bp strains in Shandong Province was ptxA1/ptxC1/ptxP1/prn1/fim2-1/fim3-1/tcfA2. After 2020, the major changes were as follows: ptxC1 shifted to ptxC4, ptxP1 shifted to ptxP3, and prn1 shifted to prn150. The genotypes of epidemic Bp strains differ from the vaccine strain, primarily marked by the replacement of ptxA2 with ptxA1. Continued surveillance of Bp antigen genotypes in Shandong Province is warranted to inform the development of new pertussis vaccines.

  • Articles
    TAO Li, NIE Guoai, ZHANG Rong, SU Xiaojian, YANG Guoping, GENG Heyuan, HE Ji, TAN Weilong, YANG Qinggui
    China Tropical Medicine. 2025, 25(8): 1037-1041. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.16

    Objective To establish a triple PCR method for the simultaneous, accurate, and rapid identification of three mosquito species, Anopheles crawfordi, Anopheles vagus, and Anopheles tessellatus. Methods Genomic DNA was extracted using a universal DNA extraction method from Anopheles peditaeniatus, Anopheles lesteri, Anopheles barbirostris, Anopheles splendidus, Anopheles maculatus, Anopheles aconitus, Anopheles crawfordi, Anopheles vagus, Anopheles tessellatus, and the concentration was determined. Primers were designed based on the mitochondrial COI gene of An. crawfordi, An. vagus, and An. tessellatus, with the other six mosquito species serving as controls. According to the primer design principles, primers capable of specifically amplifying the three species of mosquitoes were designed and synthesized by a professional institution. Single PCR was first performed using the extracted mosquito DNA as a template to verify primer specificity. Subsequently, the primer concentration, dNTPs concentration, and Taq enzyme amount in the triple PCR reaction system were optimized. The optimized PCR products were loaded following the capillary electrophoresis protocol, and the results were observed and recorded. The template DNA of An. crawfordi, An. vagus, and An. tessellatus was serially diluted 10-fold, ranging from 10 ng/μL to 10-6 ng/μL, followed by sensitivity testing via triple PCR. Results The primer concentrations for An. crawfordi, An. vagus, and An. tessellatus were the same, showed excellent specificity at an annealing temperature of 58 ℃, amplifying specific bands of 118 bp, 187 bp, and 307 bp, respectively. No bands were observed for other mosquito species or the blank control. The detection limits for An. crawfordi, An. vagus, and An. tessellatus were all 10-4 ng/μL. Conclusion This method enables the simultaneous, accurate, and rapid identification of An. crawfordi, An. vagus, and An. tessellatus samples, and is applicable to specimens with incomplete morphological features, such as damaged or non-adult stages. It provides a reliable technical tool for mosquito surveillance and disease prevention and control.

  • Articles
    TIAN Cheng, ZHEN Qian, WANG Zemin, LYU Xufeng, ZHENG Xianzhi, JIANG Xia
    China Tropical Medicine. 2025, 25(11): 1493-1498. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.20

    Objective To analyze the epidemiological and clustering epidemic characteristics of fever with thrombocytopenia syndrome (SFTS) in Changzhou City, Jiangsu Province, China, and to find out the loopholes in the disposal of the epidemic, thereby providing a scientific basis for the prevention and control of the epidemic in Changzhou City. Methods Descriptive epidemiological methods were used to characterize the case profiles across demographic, temporal, geographical, healthcare-seeking, and clustered outbreak dimensions in Changzhou City from 2021 to 2024. Between-group differences in characteristics were analyzed using chi-square tests or Fisher's exact probability tests, as statistically appropriate. Results A total of 61 SFTS cases were reported in Changzhou City from 2021 to 2024, with an incidence rate of 0.28/100 000, and a cumulative total of 17 deaths, with a case fatality rate of 27.87%. The male-to-female ratio was 1:1.03, with a median age of 66 (58.25, 72.75) years. A statistically significant difference in age distribution was observed between the clinical improvement group and the mortality group (P<0.01). The predominant occupational category among participants was farmers. The onset of the disease was mainly in summer and fall, with most of the cases concentrated in Liyang City and Jintan District, and the median time from onset to diagnosis was 5 d. 95.08% (58/61) of the cases were confirmed in tertiary and above medical institutions. Three SFTS household cluster outbreaks were reported between 2021 and 2024, of which two were caused by close caregiving during the hospitalization of relatives. Among the two primary cases, one died, while the two subsequent cases were both cured. The other cluster was caused by direct contact with the blood of the deceased and contaminated materials. The primary case died, and one of the two subsequent cases also died. Conclusion The incidence of SFTS in Changzhou City is showing an increasing and spreading trend. It is crucial to enhance health education for high-risk populations in key areas and to strengthen the case detection capabilities of primary healthcare institutions in high-incidence townships. For suspected cases, especially those at risk, viral nucleic acid testing should be conducted as early as possible; hospital discharge management and tracking should be strengthened; and infection control should be done in households and communities to prevent clustered outbreaks..

  • Articles
    WANG Qing, XIE Xiaoxin, FU Yanhua, YANG Xiaoyan, GAN Lin, MA Shujing, JIAO Pengzhu, WU Muli, LI Jun, LONG Hai
    China Tropical Medicine. 2025, 25(12): 1572-1579. https://doi.org/10.13604/j.cnki.46-1064/r.2025.12.10

    Objective To assess the trends in late presentation among HIV/AIDS patients in Guiyang City from 2012 to 2024, and to predict the number of late-detected incidents for 2025-2026, thereby providing a reference basis for the development of precise prevention and control strategies for early-detected cases. Methods The study combined descriptive epidemiological analysis with time-series forecasting. The newly reported HIV/AIDS cases in Guiyang City from 2012 to 2024 were selected from the China AIDS Comprehensive Prevention and Control Information System. The time trend of late presentation was analyzed by using the Joinpoint regression model; an Autoregressive Integrated Moving Average (ARIMA) model was used to predict the number of late presentation patients for 2025-2026. Results From 2012 to 2024, 14 128 new HIV/AIDS cases were reported in Guiyang City, and the incidence rate increased from 10.20/100 000 in 2012 to 20.09/100 000 in 2024, with an overall increasing trend [Average Annual Percent Change (AAPC)=4.16%, P<0.001]. During 2012-2024, there were 10 521 late presentation cases, with an overall late presentation rate of 74.47%, which declined slowly over time (AAPC=-1.05%, P=0.003). The proportion of late presentations was higher in the ≥50 age group (80.28%) compared to the <50 age group (71.17%), and higher for heterosexual transmission (77.87%) compared to homosexual transmission (64.58%). Joinpoint regression model analysis indicated a slow downward trend in the proportion of late presentations across different genders, age groups, and modes of transmission. The AAPCs for males, ≥50 years, and homosexual transmission were -0.81%, -0.87%, and -1.15%, respectively, with no statistically significant change. In contrast, the AAPCs for females, <50 years, and heterosexual transmission were -1.87%, -1.42%, and -1.24%, respectively (all P<0.05). Conclusion From 2012 to 2024, the overall incidence of HIV/AIDS in Guiyang showed an increasing trend. Although the proportion of late presentations has been slowly decreasing, it remains high-particularly among individuals aged ≥50 years and those infected via heterosexual transmission-who should be prioritized in HIV prevention and control. Tailored health education and optimized testing strategies should be developed for these key populations to enhance early detection.

  • Case Report
    LIU Ying, PAN Yixin, CHEN Taifang, TANG Huizhen, ZHAO Jingxian
    China Tropical Medicine. 2025, 25(9): 1225-1228. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.23

    Helsmoortel-Van der Aa syndrome (HVDAS) is a rare neurodevelopmental disorder primarily caused by mutations in the active-dependent neuroprotective protein (ADNP) gene, representing one of the most common monogenic causes of autism spectrum disorder (ASD). This retrospective analysis describes a 3-year-and-10-month-old boy with HVDAS who presented at Haikou Maternal and Child Health Hospital in 2024 with autism spectrum disorder, global developmental delay, distinctive facial features, short stature, and hydrocephalus. Genetic testing revealed a heterozygous mutation in the ADNP gene [NM_001282531.3(ADNP): c.2189 (exon 6) delG [p.(Arg730Glnfs3)]], with no family history of this mutation among his parents or sister. Summarizing the clinical data alongside a literature review, the ADNP gene plays a crucial role in chromatin remodeling and neurodevelopmental disorders, with mutations capable of affecting multiple systems. This case exemplifies the typical clinical manifestations of HVDAS while broadening the phenotypic spectrum of hydrocephalus, providing valuable insights for genetic counseling and early clinical identification of such genetic variants.

  • Topic on Dengue Fever Epidemic and Control
    WANG Rumin, WU Nanwei, CUI Lei, SUN Chuyang, TANG Yingfang, MA Yan
    China Tropical Medicine. 2025, 25(9): 1113-1118. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.05

    Objective To investigate the genetic characteristics of the envelope (E) protein gene of dengue virus type 1 (DENV-1) circulating in Hainan Province, China, in 2023, so as to provide a reference for local prevention and control of dengue fever. Methods Serum samples of suspected dengue fever cases in 2023 were collected through Hainan Province's dengue fever monitoring system. RT-PCR detected dengue viral RNA and serotype. RNA-positive samples were subjected to genome sequencing. Homology analysis and amino-acid variation analysis of the E gene were conducted by phylogenetic-tree construction. Results Thirty-eight E protein gene sequences were obtained from 49 DENV1-positive samples. Nucleotide (amino-acid) identity among the 38 sequences was 98.5%-100.0% (98.4%-100.0%). Compared with the Hawaii reference strain (AF425619.1/USA: Hawaii/1945), nucleotide (amino-acid) identity was 93.5%-94.3% (96.0%-97.0%). All 38 sequences belonged to genotype I. Among them, 37 gene sequences clustered into one sub-clade closely related to strains from Myanmar (2019) and Guangzhou, China (2023); the remaining sequence was closely related to strains from Hainan, China (2019), Singapore, Cambodia, and Haikou, Hainan (2021). Relative to the Hawaii strain, 27 of 495 amino-acid residues in the E protein were mutated, but three critical virulence residues [E44(E), E156(T), and E366(N)] and the two glycosylation sites at positions 67 and 153 were conserved. Conclusion The DENV-1 strains circulating in Hainan Province in 2023 belong to Genotype Ⅰ type, and the outbreak may involve two transmission chains. Virulence-associated and glycosylation sites remained unchanged, although multiple mutations were present in the E protein, suggesting that the virus may be under selection pressure during evolution. Therefore, it is recommended to continuously strengthen pathogen surveillance of dengue fever and implement more effective prevention and control measures.

  • Articles
    LI Juan, HUANG Wenhui, ZHA Lajia, LEI Haijuan, YAN Dong, HE Yiqun
    China Tropical Medicine. 2025, 25(12): 1559-1567. https://doi.org/10.13604/j.cnki.46-1064/r.2025.12.08

    Objective To analyze the composition and antimicrobial resistance patterns of pathogenic bacteria isolated from urine specimens in Qinghai Province from 2019 to 2024, and to provide data support for the anti-infection treatment of urinary tract infection patients in Qinghai Province. Methods Data on bacterial isolates from urine specimens were collected from 24 member hospitals of the National Bacterial Resistance Surveillance Network in Qinghai Province between 2019 and 2024. Data are presented as counts and percentages (%). The WHONET 5.6 software was utilized to analyze the species distribution and temporal changes in antimicrobial resistance patterns. Duplicate isolates (i.e., subsequent isolates of the same bacterial species from the same patient) were excluded, retaining only the first isolate for each patient. Bacterial identification was performed using automated bacterial identification systems in the microbiology laboratories of the participating institutions. Antimicrobial susceptibility testing was conducted via the micro-broth dilution method and the disk diffusion (K-B) method, with results interpreted according to the CLSI M100 (ED35) guidelines. Results A total of 26 319 bacterial isolates were obtained from urine specimens during the study period. Gram-negative bacteria accounted for 20 021 isolates (76.1%), while Gram-positive bacteria constituted 6 298 isolates (23.9%). The most frequently isolated pathogens were Escherichia coli (15 617 isolates, 59.2%), followed by Enterococcus faecium (2 055 isolates, 7.8%), Enterococcus faecalis (1 940 isolates, 7.3%), Klebsiella pneumoniae (1 330 isolates, 5.0%), Enterobacter cloacae (582 isolates, 2.0%), Proteus mirabilis (531 isolates, 1.9%), Klebsiella oxytoca (429 isolates, 1.5%), Streptococcus agalactiae (410 isolates, 1.5%), and Pseudomonas aeruginosa (339 isolates, 1.2%). Among Enterobacterales (including E. coli, K. pneumoniae, P. mirabilis, E. cloacae, and K. oxytoca), resistance rates to cefoperazone/sulbactam, piperacillin/tazobactam, imipenem, ertapenem, and amikacin were low (below 9%). In contrast, high resistance rates were observed for ampicillin (8 757 isolates, 84.8%), and cefazolin (7 771 isolates, 56.7%). P. aeruginosa exhibited low resistance to amikacin (below 3%) but higher resistance to levofloxacin (328 isolates, 18.7%). Enterococci isolates demonstrated low resistance to linezolid, vancomycin, and teicoplanin (below 2.2%). All S. agalactiae isolates remained susceptible to penicillin G, ampicillin, vancomycin, and linezolid. Conclusions From 2019 to 2024, Gram-negative bacteria were the predominant pathogens isolated from urine specimens in Qinghai Province, with no significant annual variations in the distribution of bacterial species. Clinicians should reasonably use antibiotics according to the drug sensitivity results to reduce the production of drug-resistant bacteria.

  • Topic on Dengue Fever Epidemic and Control
    CHEN Siyu, YIN Xiaoxiong, YANG Zhaolan, YAN Xiangyu, SHUI Tiejun
    China Tropical Medicine. 2025, 25(9): 1149-1154. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.11

    Objective To understand epidemiological characteristics of dengue fever in Ruili City from 2013 to 2024, to provide a reference basis for scientific control and prevention of dengue fever. Methods Information on reported dengue fever cases in Ruili from 2013 to 2024 was collected through the China Disease Control and Prevention Information System (CDCIS) and epidemiological surveys, and descriptive epidemiological methods were used to analyze the data on dengue fever cases. Brett index (BI) was used to analyze the vector Aedes larval density monitoring data, and association between the number of cases and Brett index was analyzed using Spearman correlation. Results A total of 9 122 dengue fever cases were reported in Ruili City from 2013 to 2024, including 7 128 local cases (78.14%), 18 imported cases (0.20%) within the country, and 1 976 imported cases (21.66%) from abroad, with imported cases from abroad mainly from Myanmar (99.29%, 1 962/1 976). Both local and imported cases were concentrated in August-November, and there was a significant correlation between temporal distribution (r=0.96, P<0.01). There was no statistically significant difference in gender between imported and local cases. The minimum age of the cases was 1-day-old and the maximum age was 93-years-old, and the median age of onset of the imported cases was younger than that of the local cases. The top three occupations with the highest incidence of cases were commercial services, domestic work, and students. Cases were reported in all six townships in Ruili City, with Mengmao Town (Ruili urban area) being the most predominant. Imported cases had a longer interval between onset and diagnosis than local cases. There was a significant positive correlation between the number of dengue cases and Brett index in Ruili City (r=0.82, P=0.01). Conclusion Ruili City has been experiencing local epidemics of dengue for 12 consecutive years from 2013 to 2024. At the same time, Ruili City is adjacent to Myanmar, with many border crossings, developed transportation and logistics, and frequent movement of people, the imported cases reported in Ruili City are mainly imported from Myanmar, and the situation of dengue fever control and prevention has been more severe. Strengthening the monitoring and management of cross-border transmission of dengue fever along the China-Myanmar border as well as regularization of mosquito control and prevention are the key measures to control dengue fever in the region.

  • Vector Surveillance and Control
    WANG Chunyu, ZHANG Jiayong, BAI Yuyin, DING Jun
    China Tropical Medicine. 2025, 25(11): 1451-1455. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.13

    Objective By investigation of the density distribution, population composition, and degree of infestation of cockroaches in different habitats in 14 prefecture-level cities in Liaoning Province from 2020 to 2024, this study provided a detailed analysis of the dynamic patterns of their seasonal fluctuation, and provided theoretical support for development of scientific and effective cockroaches prevention and control strategies. Methods From 2020 to 2024, the sticky trap method was used to monitor cockroaches density in six habitats including farm product markets, supermarkets, hotels, restaurants, hospitals, and residential areas in 14 prefecture-level cities in Liaoning Province. The surveillance results of cockroaches were statistically analyzed using Excel 2010 and SPSS 27.0 software. The density and species composition of cockroaches were analyzed, and the density difference and seasonal fluctuation trend of cockroaches in different years and different habitats were compared. Results A total of 19 998 cockroaches were captured in Liaoning Province from 2020 to 2024, with a cockroach density of 0.32 cockroaches per paper (19 998/63 215), and the infestation rate was 5.57% (2 707/48 616). The captured population was mainly Blattella germanica, accounting for 97.33% (19 465/19 998) of the total. The density of cockroaches in different habitats was highest in farm product markets, reached 1.25 cockroaches per paper, followed by supermarkets with a density of 0.44 cockroaches per paper, and the lowest was in hotels and hospitals with a density of 0.05 cockroaches per paper. Among the surveillance sites in the province, Yingkou had the highest density of cockroaches, reached 2.43 cockroaches per paper, followed by Tieling with a density of 0.70 cockroaches per paper, Fuxin and Jinzhou was with the lowest density of only 0.01 cockroaches per paper. Among the surveillance sites in the province, Huludao and Yingkou had relatively high cockroaches infestation rate, at 13.20% and 11.85% respectively. Jinzhou has the lowest infestation rate, at only 0.97%. The peak of cockroaches density and infestation rate occurred from July to September. The seasonal fluctuation of cockroaches density differed significantly in different years (χ2=44.504, P<0.05) and in different habitats (χ2=41.913, P<0.05). Conclusion Blattella germanica was the dominant species of cockroaches in Liaoning Province. Farm product markets and supermarkets has a relatively high density of cockroaches. Therefore, it is necessary to strengthen the monitoring and control of cockroaches in these places.

  • Zoonotic Highly Pathogenic Infectious Diseases
    CHEN Yi, SU Chao, HUANG Ying, YA Hongxiang, YANG Shiwei, YAO Shitang, TIAN Chuqi, ZHAO Ying, PU Ennian, GAO Zihou
    China Tropical Medicine. 2025, 25(8): 984-989. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.07

    Objective To investigate the species composition of rodents and their ectoparasitic fleas in Lianghe County, Yunnan Province, and to assess infection with Yersinia pestis and Rickettsia mooseri, thus providing a scientific basis for the prevention and control of local flea-borne diseases. Methods In April 2024, fleas were collected from the body surface of rodents captured by the cage-night method and clip-night method in Zhedao Town, Mangdong Town, Jiubao Town, Hexi Town, and Nangsong Town of Lianghe County, Yunnan Province, then the species of rodents and fleas were identified, and the flea infestation rate and flea index were calculated. The chi-square test and Fisher's exact probability method were employed to analyze flea infestation rates across different investigation sites. The total DNA was extracted from pooled flea samples, and ordinary PCR was applied to amplify the caf1 and pla genes of Yersinia pestis and the gltA gene of Rickettsia mooseri. Positive samples were sequenced and compared with GenBank entries, and a neighbor-joining phylogenetic tree was constructed with MEGA 6.06 software. Results A total of 163 rodents were captured in this study, belonging to 2 orders, 2 families, 8 genera, and 10 species. Rattus tanezumi (113, 69.33%) was the dominant rodent species in the area, followed by Crocidura attenuata (14), R. andamanensis (10), Mus caroli and Suncus murinus (8 each), R. nitidus (6), and four individuals of other species. A total of 127 ectoparasitic fleas were collected and classified into 1 order, 3 families, 3 genera, and 3 species. Leptopsylla segnis was the dominant local flea species, accounting for 74.02%, followed by Xenopsylla cheopis (22.05%), and Aviostivalius klossi bispiniformis (3.94%) was the least. The flea infestation rate in the residential area (38.57%) was significantly higher than in the Agricultural area (6.45%) (χ2=25.519, P<0.001). All 21 pooled flea samples were PCR-negative for Y. pestis, whereas three pools were positive for R. mooseri. The three positive gltA gene sequences (LHM10, LHM14, and LHM15) were identical, and Rickettsia mooseri gltA obtained in Lianghe County shared 99.14% identity with the Wilmington reference strain (U59714.1); phylogenetic analysis placed them in the same clade. Conclusions No Yersinia pestis infection was detected in ectoparasitic fleas in Lianghe County, Yunnan Province, but Rickettsia mooseri infection was detected, indicating an endemic focus of murine typhus in this region. Given the high density of rodents and fleas in certain areas, local residents are at risk and strengthened surveillance is warranted.

  • Reviews
    LI Zhen, DUAN Zhi, CHEN Hui, LIU Xingren, LIU Ran, YANG Hui, LIU Lingyong, WANG Ning
    China Tropical Medicine. 2025, 25(10): 1354-1358. https://doi.org/10.13604/j.cnki.46-1064/r.2025.10.20

    In recent years, co-infection with Hepatitis G virus (HGV) has increasingly been recognized as a significant factor affecting liver and immune functions in individuals infected with the Human Immunodeficiency Virus (HIV). The high prevalence of HGV among HIV-infected individuals, along with the complexity of its immunological mechanisms, suggests that HGV may decelerate the progression of HIV through mechanisms such as immune evasion, cytokine imbalance, and impacts on liver function. This review details the immunological mechanisms underlying HGV and HIV co-infection, with a focus on how HGV potentially slows HIV clinical progression by suppressing immune system functionality and altering the distribution of immune cell subsets. Additionally, it summarizes diagnostic approaches for this co-infection along with their limitations, and analyzes challenges in HGV detection and the application of emerging technologies; it also discusses current treatment strategies, emphasizing the importance of personalized treatment plans on top of antiretroviral therapy for optimizing clinical management. This article aims to provide new perspectives on understanding the immunological characteristics and clinical management of HGV and HIV co-infection and looks forward to potential breakthroughs in early diagnosis, immunotherapy, and personalized treatment approaches.

  • Research Reports
    LIU Huan, GAO Wanying, WU Zongzhen, XIANG Qiangyu, ZHANG Lu
    China Tropical Medicine. 2025, 25(8): 1075-1081. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.22

    Objective This article traces the discovery history and epidemic situation of schistosomiasis in Wuhu area, explores the scientific control efforts and phased achievements from 1951 to 2024, and summarizes the prevention and control technologies and practical methods that were first explored and applied locally. It outlines the evolution of three main stages: a comprehensive prevention and control phase centered on Oncomelania hupensis eradication, a chemotherapy-based control phase, and a transmission-source control phase. Methods From the perspective of the history of science and technology, this study uses historical literature review and comparative analysis to examine three stages of schistosomiasis control: comprehensive control centered on Oncomelania hupensis eradication, key control based on chemotherapy, and precision control focusing on transmission-source management, and to evaluate their influencing factors and effectiveness. Results The study highlights the extensive experience Wuhu area has accumulated in Oncomelania hupensis management and population treatment, such as health education, feces management, and "one village, one policy", which has strengthened comprehensive management capabilities. Conclusion Through examining the historical evolution of schistosomiasis prevention and control and its influencing factors in Wuhu area, these practices offer valuable lessons for other lake-type, hilly-type, and water network-type epidemic areas in China, deepen the understanding of local public health governance experience, and provide practical support and scientific reference for current schistosomiasis prevention and control initiatives.

  • Vector Surveillance and Control
    ZHONG Wenbing, DONG Haowei, YANG Xinyan, SUN Dingwei, LIN Chunyan, CHEN Jinyan, LIU Puyu, YANG Anjie, MA Yajun, PENG Heng
    China Tropical Medicine. 2025, 25(11): 1376-1381. https://doi.org/10.13604/j.cnki.46-1064/r.2025.11.02

    Objective To study on ecological niches of sandflies, and classify their species in Hainan Island, provide a scientific basis for risk assessment of sandfly-borne diseases and the development of targeted prevention and control strategies in tropical regions of China. Methods In response to the diverse geographical environment of Hainan Island, a sandfly investigation were conducted across 11 towns in 7 counties in Hainan Island from 2023 to 2024. Light trap method was used to catch sandfly samples, with environmental observations. The morphological characteristics of cibarium, pharyngeal armature, spermatheca, and male external genitalia of sandfly specimens were observed and recorded under a microscope to identify species. Results The sampling sites were located between 109°-110° E longitude and 19°-20° N latitude in Hainan Island, spanning mountainous regions, hilly areas, and plains, with an altitude ranging from 3.0 to 314.2 m. Total of 969 samples were captured, with no significant differences in collection numbers across different topographical units. Investigation and statistical results showed that the main blood-sucking and resting habitats of sandflies were poultry sheds and livestock pens. Sandfly density in poultry sheds (including adjacent storage areas, 0.4-69.0 flies/(trap·night) was significantly higher than that in livestock pens (0-7.0 flies/trap/night) (Mann-Whitney U, P=0.000 3). Number of 144 sandfly specimens was classified, as five species belonging to two genera: Phlebotomus stantoni (n=22), Sergentomyia bailyi (n=37), Se. hivernus (n=26), Se. iyengari (n=55), and Se. squamipleuris (n=4). The Sergentomyia hivernus is a new record in China. The morphological identification characteristics for the five species were supplemented and revised. Female Se. iyengari with Se. hivernus can be distinguished by the following four features: pigment patch shape (tangerine-segmented vs mushroom-shaped), arrangement of chitinous dots (2-3 rows vs 1 row), spermatheca morphology (long cylindrical vs. sausage-shaped), and degree of spermathecal head sunken (completely sunken vs. slightly sunken). Conclusion This study confirmed that poultry sheds and livestock pens are the primary blood-sucking and resting habitats for sandflies, and there are five species belong to subfamily Phlebotominae in Hainan Island, Se. hivernus is new Chinese record.

  • Zoonotic Highly Pathogenic Infectious Diseases
    LI Liuxing, LI Nan, HE Yuwen, MENG Jinxin, YANG Shaochang, WANG Jinglin
    China Tropical Medicine. 2025, 25(8): 945-950. https://doi.org/10.13604/j.cnki.46-1064/r.2025.08.01

    Objective To determine the viral carriage profiles of Rousettus leschenaultia in Yunnan, China, characterize a newly identified bocavirus (BoV), and elucidate its phylogenetic relationship, thereby providing new insights into viral source tracing and the prevention and control of associated diseases. Methods In September 2019, bats were captured from an orchard in Shuangjiang, Lincang City, Yunnan Province. After morphological identification, each bat was dissected to collect lung tissue, intestinal tissue, and intestinal contents. Homogenates were prepared from these tissues, and 200 μL of supernatant from each bat was pooled into two composite samples (pulmonary and intestinal). Samples were subjected to ultracentrifugation to concentrate viral particles, followed by nucleic acid extraction using a standardized viral RNA isolation kit. Viral nucleic acids were subjected to random PCR amplification, followed by high-throughput sequencing and de novo assembly of the amplicons. Based on the viral sequences obtained from contig assembly, primers were designed, followed by semi-nested PCR amplification and sequencing validation. Sequence alignments and phylogenetic reconstruction of the VP1 gene sequences were conducted using MEGA-X software with the neighbor-joining method. Results Five Rousettus leschenaultii were collected. A single 3 401-nucleotide (nt) contig was assembled from the intestinal composite sample, exhibiting 63.90% amino acid identity to the closest known bocaviruses by BLASTx analysis. No BoV-related sequences were detected in pulmonary tissues. Based on this sequence, five pairs of primers were designed to perform semi-nested PCR amplification on the intestinal tissues and contents of the five bats, respectively. Among these, positive amplification was observed in the intestinal tissues and contents of one Rousettus leschenaultii (ID: YNSJ03). Subsequent amplification yielded a 2 900-nt partial genome, designated YNSJ03-BtBoV. Phylogenetic analysis based on VP1 amino-acid sequences placed YNSJ03-BtBoV on an independent branch, closely related to Chinese bat bocaparvoviruses reported in 2017 and 2024. It shared 70.1% amino acid identity with BtMf-PV/HuB2013 strain and 71.0% nucleotide identity with YN2016 strain. Conclusion This study reports a novel bocavirus (YNSJ03-BtBoV) in the intestines of Rousettus leschenaultia in Yunnan, significantly expanding the known genetic diversity of bat-associated bocaviruses and providing critical insights into their evolutionary dynamics within zoonotic reservoir hosts.

  • Topic on Dengue Fever Epidemic and Control
    LU Jingjing, XING Kongzhong, CAO Li, QIU Li, TAN Gaoling, WU Song, LI Weixia, JIN Yan
    China Tropical Medicine. 2025, 25(9): 1100-1107. https://doi.org/10.13604/j.cnki.46-1064/r.2025.09.03

    Objective To investigate the initial transmission dynamics at the early stage of a dengue fever outbreak in Hainan, this study aimed to trace the epidemic's onset time, evaluate the effectiveness of implemented prevention and control measures, and explore optimized intervention strategies, thereby providing a theoretical basis for the scientific control of dengue fever. Methods A coupled human-mosquito transmission dynamics model was used to investigate dengue transmission patterns. Model parameters and the onset time of the epidemic were estimated using a combination of numerical simulation and optimization techniques. First, parameters were randomly sampled from a uniform distribution, and for each sample, the differential equations were solved with the fourth-order Runge-Kutta method. The parameter set yielding the minimum Root Mean Square Error (RMSE) was considered optimal. This procedure was repeated, and the median of the resulting optimal parameter sets was taken as the final best estimate. The transmission potential was further assessed through the basic reproduction number R0 Additionally, simulation modeling quantified the effectiveness of three key interventions, including personal protection combined with environmental management u1, larval mosquito control u2, and adult mosquito control u3. Results The estimated onset time of this epidemic was August 15, predating both the first symptom onset and case reporting date. The mosquito-to-human transmission rate was estimated to be 0.85 (95% CI: 0.79-0.88), and the human-to-mosquito transmission rate was 0.93 (95% CI: 0.87-0.97). The implemented control measures were estimated to have reduced the total number of infections by 53.6% compared to the no-intervention scenario. During the early epidemic phase without interventions, R0 reached a maximum value of 2.48 at 29.0℃ and a minimum of 1.47 at 23.5 ℃. Following the implementation of control measures on September 20, R0 declined to 0.42 at 23.5 ℃ and 0.98 at 29.0 ℃, respectively. Simulations of the combined three-measure strategy (u1, u2, and u3), initiated 4 days earlier with respective coefficients of 0.2, 0.15 and 0.06, projected an 49.0% reduction in cumulative new cases and shortened the epidemic's duration by 5 days compared to the no-intervention scenario. Conclusion Prior to the first confirmed case being identified, dengue fever had already been circulating cryptically within the community. Without intervention measures, Hainan's meteorological conditions exacerbated the potential for epidemic transmission. The implemented interventions proved highly effective, significantly reducing case numbers, shortening the duration of the outbreak, and curbing further transmission. Among these measures, the combination of personal protection, environmental management, and adult mosquito control proved to be highly effective. Consequently, future strategies should prioritize vector-targeted interventions, integrated with personal protection and environmental management, to establish a multi-tiered defense framework.