Volume 14 · Issue 05 · 2025

As of July 22, 2025, the chikungunya virus transmission has been documented across 119 countries and territories of the world. In 2025, an outbreak of chikungunya fever (CF) occurred in Foshan, Guangdong Province, China. We aimed to analyze the epidemiological characteristics and transmission dynamics during the early stage of this outbreak.

We collected the data of CF cases in Foshan from July 8 to July 26, 2025. Case data were extracted from the National Notifiable Infectious Disease Reporting System. Demographics and tempo-spatial distributions of cases, incidence rates and the onset-to-report interval times were analyzed. Global spatial autocorrelation (Moran’s I) to assess township-level clustering; Kruskal-Wallis tests with Dunn’s post-hoc comparisons (Bonferroni-corrected) to analyze onset-to-report intervals across four epidemic phases. The basic reproduction number (R₀) was calculated using a maximum likelihood method, which was also compared with the R₀ from the CF outbreak in Dongguan City of Guangdong Province in 2010.

A total of 4754 local cases were reported during the study period. Persons aged 65 years or above had the highest incidence (116.57 per 100,000 population). Most cases were business/service workers, homemakers, and retirees. The median onset-to-report interval decreased from 4 days to 1 day after outbreak control measures were implemented. The outbreak, initially detected in Shunde District, spread rapidly to other districts of Foshan, forming a significant spatial cluster (Moran’s I = 0.152, P = 0.029). The estimated R₀ was 16.3 (95% confidence interval: 15.0 to 17.5), substantially higher than the estimated R₀ of 5.5 for the Dongguan outbreak in 2010.

This outbreak was characterized by high transmissibility, with older persons being a primary high-risk group. The rapid reduction in case reporting delay highlights the effectiveness of response interventions. Sustained, integrated and prompt response has been essential to control the outbreak.

Following the onset of an index chikungunya case on July 8, 2025, a significant outbreak occurred in Foshan, Guangdong Province, China. This study aimed to quantify the outbreak’s transmissibility between June 16 and July 21, 2025.

Data were obtained from local Government, Statistics Bureau, Centers for Disease Control and Prevention, and the relevant literature. We employed a transmission dynamic model that integrated human host-vector transmission to estimate the basic reproduction number (R₀). The key parameters of the model were calibrated using early-phase limited surveillance data on the cumulative number of cases. We calculated the correlation coefficient to evaluate the accuracy of this calibration. Sensitivity analyses were conducted to quantify the uncertainties in the parameter inputs.

Between June 16 and July 31, 2025, cumulative cases reached 2658, with 92.96% concentrated in the Shunde District. Model simulations showed that a cumulative case count is consistent with local reports (Pearson r = 0.99, P < 0.001). The median overall R₀ of this outbreak was 7.2807 [interquntile range (IQR): 7.2809-7.2811], suggesting sustained transmission. Human-to-mosquito transmission (Median: 22.79, IQR: 5.44-40.14) had a higher median R₀ than mosquito-to-human transmission (Median: 2.33, IQR: 0.58-4.07) (Mann-Whitney U P < 0.001). Symptomatic infections (Median: 19.60, IQR: 4.68-34.52) had a higher median R₀ than asymptomatic infections (Median: 3.19, IQR: 0.76-5.62) (Mann-Whitney U P <0.001). The model simulated cumulative cases were sensitive to parameters a, b, ω_m, and ω_p. The overall R₀ and mosquito-to-human R₀ were sensitive to parameters a and b. The human-to-mosquito and symptomatic human-to-mosquito R₀ were sensitive to parameter γ, while asymptomatic human-to-mosquito R₀ was sensitive to parameter ω_p′.

The transmissibility of CHIKV is high. Human-to-mosquito transmission, especially symptomatic infections to mosquito transmission, was the main driver of chikungunya virus transmission. These findings underscore the critical need for enhanced screening of travellers from endemic regions, timely case isolation, and targeted vector control to mitigate autochthonous transmission.

Since July 2025, an outbreak of mosquito-borne chikungunya fever has occurred in Foshan City, Guangdong Province, China. This was the second large-scale local outbreak in China after the one that occurred in Dongguan City, Guangdong Province, in 2010. As of 23 August, more than 10,000 human cases had been reported. This study aims to investigate mosquito infection and viral genomic characteristics during the Foshan outbreak.

Adult Aedes albopictus were collected using BioGents Sentinel trap in three hotspot towns (Beijiao, Chencun and Lecong). Mosquitoes were morphologically identified and pooled by species, sex and environment type. Each pool was homogenized, and the homogenate was clarified by centrifugation; and the supernatant was used for viral RNA isolation. The isolated RNA was screened using CHIKV RT-qPCR. Positive pools underwent Sanger sequencing and whole-genome sequencing. The CHIKV lineage and mutational profiles were inferred using maximum likelihood phylogenetic analysis and comparison with human- and mosquito-derived genomes.

Over 11 days of trapping, 2803 mosquitoes were captured. 1569 (55.97%) female Ae. albopictus were divided into 77 pools and 9.09% (7/77) of these pools were CHIKV-positive. The minimum infection rate (MIR, per 1000 females) for local Ae. albopictus was 4.46, while the MIR for residences in Lecong Town was the highest at 9.17 per 1000 females. The MIR for parklands was slightly higher than for residences (4.60 vs. 4.30 per 1000 females). Five complete Ae. albopictus-derived CHIKV genome clustered within the East/Central/South African-Indian Ocean lineage genotype, and harbored novel E1 and E2 mutations consistent with those detected in the 2025 Reunion Island human strain. Amino-acid mutations E1-A226V/E2-L210Q were detected, enhancing adaptability to Ae. albopictus and increasing the transmission capacity.

This study represents the first mosquito-derived CHIKV whole-genome sequence obtained from the 2025 Foshan outbreak. Ae. albopictus was confirmed as the primary vector, and the presence of adaptive mutations indicated an enhanced transmission potential. Despite the outbreak emerging earlier in the season and affecting a dense urban population, it was effectively controlled through timely and intensive vector interventions. These findings highlighted the critical role of mosquito surveillance in early outbreak preparedness and effective vector management.

Opisthorchiasis infected by Opisthorchis felineus has represented a significant but understudied public health issue for the population residing in Western Siberia and the Ural Region of the Russian Federation. This study aimed to produce high-resolution spatial-temporal disease risk maps for guiding prevention strategy in the above region.

Data on prevalence and surveillance data reflecting reported annual incidence rate of O. felineus infection in the study region were collected through systematic review and the annual reports of the Ministry of Health of the Russian Federation. Environmental, socioeconomic and demographic data were downloaded from different open-access data sources. An advanced multivariate Bayesian geostatistical modeling approach was developed to estimate the O. felineus infection risk at high-resolution spatial-temporal by joint analysis of survey and surveillance data, incorporating potential influencing factors and spatial-temporal random effects. The annual spatial-temporal risk maps of O. felineus infection at a resolution of 5 × 5 km² were produced.

The final dataset included 76 locations of survey data and 303 locations of surveillance data on O. felineus infection. The infection risk was high (> 25%) in most part of central and eastern regions, and relatively low (< 25%) in most part of western region, while temporal variations were observed across the sub-regions in recent decades. Particularly, in the densely populated eastern region, there was an increased trend of infection risk from 30.46% (95% Bayesian credible intervals, BCI 10.78-53.45%) in 1980 to 53.39% (95% BCI 13.77-91.93%) in 2019 and gradually transformed into high-risk. In the study region (excluding the western region due to data sparsity), the population-adjusted estimated prevalence was 46.61% (95% BCI 15.09-76.50%) in 2019, corresponding to approximately 7.91 million (95% BCI 2.56-12.98 million) people infected.

The high-resolution risk maps of O. felineus in Western Siberia and the Ural Region of the Russian Federation have effectively captured the risk profiles, suggesting the infection risk remains high in recent years and providing substantial evidence for spatial-target control and preventive strategies.

Although France is considered a low tuberculosis (TB) incidence country, TB remains a significant public health issue in certain high-risk groups and geographic areas, potentially linked to socioeconomic determinants. This study aims to assess the associations between TB notification rates and area-level socioeconomic variables in metropolitan France.

We conducted an ecological spatial study using TB cases reported to the French national surveillance system from 2008 to 2019. Using Bayesian Poisson regression, we modeled TB case counts at the ZIP code level. Standardized notification rates were estimated through indirect standardization by age, sex, immigration status, and housing type. The model included ZIP code level socioeconomic variables and a spatial random effect to account for spatial autocorrelation and residual variations in notification rates, which may relate to territorial disparities in reporting completeness.

The study included 55,330 reported TB cases across 4478 of 5534 ZIP codes in metropolitan France. All tested socioeconomic variables showed varying associations with TB. In the multivariable model, an increase in population density from 'Low’ to 'High’ was associated with a 30% increase [95% credible interval (CrI): 21%, 38%] in standardized TB notification rates. An increase from the first to the ninth decile in the unemployment rate among those aged 15-64 was associated with a 28% increase (95% CrI: 19%, 37%). Similarly, an increase in the proportion of overcrowded households was associated with a 19% increase (95% CrI: 11%, 28%). Conversely, an increase in median household income was associated with a 7% decrease (95% CrI: 1%, 11%).

Our findings suggest that TB notification rates are independently associated with material deprivation, such as unemployment and low income, as well as crowded settings, including overcrowded households and densely populated areas. Enhancing TB control in metropolitan France could involve targeted outreach programs for screening and treatment in materially deprived areas, characterized by high unemployment rates and low median incomes, and adopting a 'Health in All Policies’ approach to address urban and household crowding.

Hemorrhagic fever with renal syndrome (HFRS) poses a significant public health concern in China. However, the spatiotemporal patterns and underlying drivers of its transmission are not fully understood. This study aims to investigate spatiotemporal heterogeneity of HFRS incidence at the city level and explore its potential influencing factors.

Joinpoint regression was utilized to analyze city-level HFRS incidence data (n = 314 cities, 2005-2021) collected from the National Infectious Disease Surveillance System. Furthermore, we employed the Geodetector method to identify the potential driving factors from a set of meteorological, vegetation, and urbanization variables.

The results from Joinpoint regression analysis revealed an overall declining trend in city-level HFRS incidence across China from 2005 to 2021. Of the cities analyzed, 126 showed an upward trend [the average annual percent change (AAPC) >0], 176 a downward trend (AAPC < 0), and 12 remained stable (AAPC = 0). Notably, upward-trend cities were predominantly concentrated in South China. Geodetector analysis indicated that selected climatic and vegetation factors accounted for 19-56% of the spatiotemporal heterogeneity in HFRS incidence, whereas urbanization factors explained only 3-5%. However, synergistic interactions between temperature and urbanization-related variables (i.e., land-use, economic, and demographic dimensions) significantly enhanced their explanatory power, particularly in upward-trend cities, where the combinations increased explanatory capacity by 124-184%.

In summary, while climatic and vegetation factors remain the primary drivers of the spatiotemporal heterogeneity of HFRS epidemics in China, urbanization also exerts non-negligible influence on city-level incidence. This research offers valuable insights for public health authorities to strengthen their intervention capabilities against this disease.

Whole blood samples are often used to generate whole genome sequences, which provide valuable insights into the genetic make-up of viruses. However, the collection and management present significant challenges, particularly in remote and resource-limited communities, where maintaining a cold chain is often difficult and costly. The use of dry blood spots (DBS) is gradually increasing to overcome these logistical barriers with reduced biosafety constraints. We propose an alternative approach using native DBS Lassa virus (LASV)-positive samples as a substitute for whole blood.

Next-generation sequencing (NGS) was performed on RNA extracted from whole blood and DBS samples using Illumina technology. RNA concentration, cycle threshold (Ct) values and sequence read counts were statistically compared. A total of 78 samples from 39 LASV-positive Mastomys atalensis were analysed. Whole blood had significantly higher mean RNA concentration (26.5 ± 1.9) than DBS (3.4 ± 0.3), P < 0.05. Mean Ct values in whole blood were significantly lower than in DBS (P = 0.0001). Log mean sequence reads and NGS coverage for both S and L segments were significantly higher in whole blood (P = 0.0001). RNA concentration showed no association with sequence coverage (P = 0.382), while Ct values showed a strong association (P = 0.0001).

Our study demonstrates that DBS is a viable alternative for whole genome sequencing of LASV, although whole blood samples consistently outperform DBS in terms of RNA concentration, Ct values and NGS coverage.

Schistosomiasis, an infectious disease of poverty, remains a public health challenge worldwide. Although praziquantel chemotherapy has been proven to be an effective antiparasitic intervention, real-world evidence indicates that in patients with hepatointestinal schistosomiasis, hepatic fibrosis may continue to progress even after treatment. The current understanding of the mechanisms underlying persistent liver fibrosis progression in Schistosoma-infected individuals post-treatment is unclear. The aim of this commentary is to analyze the critical yet multifactorial determinants contributing to the persistent progression of liver fibrosis and to advocate for a comprehensive research focus to support the global elimination of this disease.

Multiple mechanisms may contribute to the persistent progression of liver fibrosis in schistosomiasis. These include the continued presence of viable Schistosoma eggs, co-infection with hepatitis viruses, alterations in splenic structure and function, disruption of the intestinal mucosal barrier, hepatic ischemia and hypoxia, hepatocyte death, specific types of collagen deposition, and host genetic variations. However, additional factors potentially contributing to host pathology warrant further investigation.

In the post-schistosomiasis control era, expanding the focus of research to include the "post-treatment" phase is essential. Investigating the mechanisms underlying the persistent progression of liver fibrosis and identifying future research priorities may enhance efforts toward the global elimination of schistosomiasis and improve long-term health outcomes for individuals who have received praziquantel treatment.