In China, waterborne transmission is a relatively rare route for norovirus outbreaks; however, once it occurs, the outbreaks tend to be large in scale, prolonged in duration, and difficult to control. This systematic review characterizes the epidemiological features of such outbreaks in China. We searched the WANFANG, CNKI, PubMed, and Web of Science databases for literature on waterborne norovirus outbreaks published up to November 2023. From 2000 to 2022, a total of 112 outbreaks were reported in China among the 97 articles included. These outbreaks involved approximately 19,796 cases and 565,485 exposures, median of 98 cases per outbreak, with a median attack rate of 6.09 %. Most outbreaks occurred in southern regions, particularly in coastal provinces, with schools (59, 52.68 %) and towns or villages (25, 22.52 %) being the most common settings. The highest number of outbreaks was reported in February and the lowest in July, with an average of 8.25 outbreaks per month. Higher attack rates were associated with outbreaks occurring in winter, in primary schools, and in southern regions of the Qinling-Huaihe line. Contamination of barreled water and self-provided wells was the primary risk factor for waterborne norovirus outbreaks. Although waterborne transmission is a relatively rare route for norovirus outbreaks in China, it can cause large-scale outbreaks in a short period. Consequently, it is still necessary to enhance protection of water sources, rigorous water quality monitoring, and public health education on water sanitation.

Cases of scarlet fever have increased since 2011 across China. However, genomic epidemiological knowledge of Streptococcus pyogenes, the causative agent, is limited. Here we present a longitudinal analysis of S. pyogenes isolates (n = 1,029) across emm1 and emm12 genotypes collected from eight provinces across China between 1993 and 2024. Genomic data integrated with national scarlet fever incidence data confirmed emm12 and emm1 as dominant genotypes underlying five incidence peaks and disease resurgence in 2024. Phylogenetic analysis showed independent evolution of these genotypes in China compared to global epidemic lineages. Four emm12 clades were present in China before 2011 but were replaced by a single clade, Clade II, by 2020. A dominant emm1 clade, M1china, distinct from global lineages and the M1UK lineage, represents >98% of emm1 cases in China. Sub-clade expansion coincides with carriage of integrative conjugative elements containing macrolide and tetracycline resistance genes and virulence gene-encoding prophage. Ongoing maintenance of these elements in emm1 and emm12 populations likely underlies the resurgence of scarlet fever in China.

Abstract Background Hand, foot, and mouth disease (HFMD) is a common enteric infectious disease that poses a threat to children’s health. The disease exhibits high epidemic intensity and frequent outbreak clusters in Beijing, the capital of China. However, the spatiotemporal characteristics of these outbreak clusters and their future epidemic trends remain poorly understood. This study aims to fill this gap by analyzing the spatiotemporal epidemiology of HFMD outbreak clusters and developing a forecasting model to inform targeted prevention strategies. Methods The present study analyzed data on HFMD outbreak clusters in Beijing from 2019 to 2024. Epidemiological characteristics were described, including demographic features, clinical manifestations, transmission settings, and spatial distribution. Group comparisons were performed using Kruskal-Wallis and chi-squared tests. The spatial distribution of outbreak clusters was visualized and analyzed by geographic region. A Seasonal Autoregressive Integrated Moving Average (SARIMA) model was developed to forecast incidence trends. Results Beijing reported 4,265 HFMD outbreak clusters (12,396 cases) during 2019–2024, exhibiting a biennial high-incidence pattern. Compared to 2019 (1,206 clusters), the mean annual clusters during 2020–2022 decreased by 74.4% (305/year), rebounding to 1,719 clusters in 2023—42.5% higher than 2019. Most clusters (77.2%) involved < 5 cases. Median age was 5 years (IQR: 4–7), increasing to 6 years in 2023. Males predominated (p < 0.001). School-aged cases rose to 54.4% in 2023, while kindergarten cases declined. Kindergartens predominated overall (52.7%), but schools became the main setting in 2023 (44.9%), 4.2 times the pandemic average (10.6%). Clusters concentrated in near-suburban areas (> 50% in multiple years). CV-A6 was dominant (60.2%), peaking at 90.7% in 2023; EV-A71 was rare (0.12%). Cluster size varied by pathogen (p < 0.001). The SARIMA model forecast a bimodal pattern for 2025, with primary autumn peak (299 clusters) and secondary summer peak (165 clusters). Conclusion HFMD outbreak clusters in Beijing exhibited a biennial pattern, with suppression during 2020–2022 due to COVID-19 NPIs followed by a rebound in 2023 exceeding pre-pandemic levels. Clusters concentrated in near-suburban areas with consistent bimodal seasonality, and the SARIMA model projects a similar pattern for 2025. These findings underscore the need for setting-specific strategies prioritizing schools alongside kindergartens, targeted interventions in high-risk suburbs, and continued pathogen monitoring.

BACKGROUND:Data on influenza vaccine effectiveness (VE) against hospitalized severe acute respiratory infection (SARI), particularly in Asia, remain limited for the 2025/26 Northern Hemisphere influenza season. This study aimed to evaluate real-world VE against A(H3N2)-associated SARI hospitalization and provide timely, locally relevant evidence to inform seasonal influenza vaccination policy. METHODS:A test-negative design was used to estimate VE against influenza A(H3N2)-associated SARI hospitalization in Beijing, China, from 10 November 2025 to 18 January 2026. VE was estimated by comparing the odds of influenza vaccination between case-patients (those who tested positive for A(H3N2)) with controls (those who tested negative for influenza). RESULTS:Among 1883 enrolled SARI inpatients, 220 (11.7%) tested positive for influenza A(H3N2). Overall vaccination coverage was 11.4%, with the highest coverage observed among children aged 5-17 years (29.6%). Influenza positivity was higher among rural residents, patients with pneumonia or hypoxemia, and those with symptom onset in November. The adjusted overall VE was 7.5% (95% CI: -45.8% to 43.3%). Moderate VE was observed among children aged 5-17 years (45.4%, 95% CI: -33.6% to 79.5%), although the confidence interval included zero and the estimate was not statistically significant. Negative VE estimates were observed among younger children and older adults. Among patients with underlying respiratory conditions, VE was 75.4% (95% CI: -27.4% to 98.7%), although this estimate was also not statistically significant. CONCLUSIONS:During the 2025/26 influenza season in Beijing, VE against A(H3N2)-associated SARI hospitalization was suboptimal. Moderate protection was observed among children aged 5-17 years, the group with the highest vaccination coverage, but the estimate was not statistically significant. The low overall VE may be attributable to antigenic mismatch between vaccine and circulating strains, as well as low population-level vaccination coverage. These findings highlight the need to improve vaccine formulations and increase vaccination coverage, particularly among adults and older populations.

BACKGROUND:Hand, foot, and mouth disease (HFMD), particularly EV-A71, has caused large-scale epidemics in the Asia-Pacific region, with China alone reporting over 2 million annual cases and causing a substantial morbidity and mortality. While EV-A71 vaccination was introduced in 2016 and COVID-19 non-pharmaceutical interventions (NPIs) were implemented from 2020-2022, comprehensive evidence on their independent and combined effects on HFMD epidemiology remains scarce. We aimed to quantify the impact of vaccination, NPIs, and post-pandemic policy relaxation on HFMD incidence and pathogen distribution. METHODS:We conducted an interrupted time series segmented regression analysis using a 14-year surveillance dataset (January 2011-December 2024) from Beijing's National Notifiable Disease Reporting System and citywide pathogen surveillance network. The study population included all HFMD cases reported in Beijing. We defined four intervention periods: baseline (pre-vaccination), vaccination introduction (August 2016), stringent NPIs (January 2020), and reopening (January 2023). Primary outcomes were HFMD incidence rates and incidence rate ratios (IRRs). We estimated prevented cases under counterfactual scenarios. RESULTS:Among 324,623 reported HFMD cases across the 14-year study period, interrupted time series regression demonstrated that vaccination was associated with a 33% reduction in incidence (IRR 0.67, 95% CI: 0.49-0.91); cumulatively over 8 years (2016-2024), this was estimated to have prevented 23.8% of cases that would have occurred without vaccination. Stringent NPIs were associated with an 84% reduction (IRR = 0.16, 95% CI: 0.06-0.41); cumulatively, during the intervention period (2020-2022), NPIs were estimated to have prevented 82.6% of cases. Following policy relaxation, incidence rebounded 2.53-fold (95% CI: 0.64-9.92), although this increase did not reach statistical significance. In absolute terms, monthly mean case counts declined from 3001 (baseline) to 1886 following vaccination introduction (37.2% decrease), and further to 299 during stringent NPIs (90.0% decrease from baseline), before surging to 1503 post-reopening, a fivefold increase from the NPI period. Pathogen surveillance revealed EV-A71 prevalence declined from 30.5% (baseline) to 4.5% (vaccination period), while coxsackievirus A6 emerged as the dominant serotype, from 9.5% (baseline period) to 56.2% (vaccination period). CONCLUSIONS:EV-A71 vaccination and NPIs were each associated with reduced HFMD transmission, but policy relaxation was followed by a substantial resurgence. The observed serotype replacement with non-vaccine-type enteroviruses highlight critical gaps in current prevention strategies. Sustaining HFMD control requires optimizing vaccine design, developing multivalent vaccines, maintaining high coverage, and integrating targeted NPIs during high-transmission seasons.

Noroviruses are a major cause of acute gastroenteritis worldwide. In Beijing, norovirus GII.17 outbreaks, which dominated in 2014-2015 (66.7%), surged again from 1.3%-12.2% (2015-2024) to 81.7% (2024-2025), with reported outbreaks during July 2024-February 2025 dramatically exceeding the prior year (301 vs. 103). From 2014 to 2025, 249 GII.17 outbreaks were identified, comprising 107 Kawasaki308 (1525 cases) and 142 Romania-2021 (1840 cases) based on phylogenetic analysis. The proportion of outbreak settings differed for Romania-2021 and Kawasaki308: kindergartens (35.2% vs. 37.4%), primary schools (46.5% vs. 29.0%), middle schools (5.6% vs. 12.1%) and others (12.7% vs. 21.5%). Romania-2021 cases were younger and had more vomiting than Kawasaki308 cases. Phylogenetic analysis revealed that novel GII.17 strains dominated in Beijing in 2024-2025 clustered with contemporaneous global strains, forming a distinct subcluster (New_2023-2025) within New (Romania-2021 like) cluster. This subcluster exhibited unique amino acid substitutions in VP1, VP2 and non-structure proteins compared to other clusters and New subclusters. Our findings confirm the dominance of Romania-2021 like strains during 2024-2025 in Beijing. Differences in symptom profiles and affected age groups between Kawasaki308 and Romania-2021, and unique amino acid substitutions may help explain the rapid predominance of the emerging cluster.

Norovirus is the leading cause of acute gastroenteritis outbreaks worldwide. A total of 1859 norovirus outbreaks were reported from 2016 to 2022 in Beijing, China. GII.2[P16] was the predominant genotype during 2016-2021, and GII.3[P12] during 2021-2022. In the early stage of the COVID-19 epidemic (January to June of 2020), strict prevention and control measures were implemented, and only eight norovirus outbreaks were reported. Most norovirus outbreaks occurred in schools (95.6%, 1778). As the level of schooling rises, the scale of norovirus outbreaks also increases (median case numbers: 8 for kindergarten, 10 for primary school, 11 for secondary school, and 14 for college; p trend < 0.001), while the attack rate decreases (median attack rates were correspondingly 25.8%, 17.5%, 10.0%, and 8.8%; p trend < 0.001). Compared to outbreaks caused by person-to-person transmission, foodborne and waterborne outbreaks are larger in scale. Delayed outbreak response is also a risk factor for larger-scale outbreaks. Norovirus outbreaks have emerged as a significant concern for public health in Beijing. Persistent genotyping efforts are essential to facilitate early warning. Outbreaks in different locations or through different transmission routes require specific prevention and control measures.

During the early 2025/26 influenza season, influenza A(H3N2) subclade K rapidly predominated in Beijing, China. Using a test-negative design, we estimated influenza vaccine effectiveness (VE) among influenza-like illness outpatients tested between weeks 40/2025 and 04/2026. Among 10,484 participants, sequencing of 316 randomly selected A(H3N2)-positive samples showed 84.8% were subclade K, and antigenic analysis of 65 viruses indicated antigenic divergence. Despite this, adjusted VE against laboratory-confirmed influenza was 23.5% (95% confidence interval: 11.7–33.7), indicating modest protection during this subclade K-dominated season.

Objectives:To analyze the epidemiological characteristics and estimate the incidence of infectious diarrhea in Beijing, China, 2015-2019. Methods:From January 2015 to December 2019, stool specimens and epidemiological data of diarrhea cases were collected from sentinel hospitals across all districts. Viral pathogens were detected by real time PCR or RT-PCR, including rotavirus, norovirus, astrovirus, adenovirus and sapovirus. Bacterial pathogens were detected using culture, biochemical and serological assays, including Vibrio cholerae, Shigella, Salmonella typhi and Salmonella paratyphi, diarrheagenic Escherichia coli (DEC), non-typhoidal Salmonella (NTS), Vibrio parahaemolyticus, Campylobacter and other bacteria. Descriptive statistics and a Monte Carlo multiplier model were applied for analysis and incidence estimation. Results:A total of 27,804 outpatients were included from 2015 to 2019. Among cases tested for viral pathogens (N = 9,351), norovirus (1,572/9,351, 16.81%) was the most prevalent, followed by rotavirus (907/9,351, 9.70%). Among those tested for bacterial pathogens (N = 20,741), diarrheagenic Escherichia coli (DEC) (1,941/20,741, 9.36%) was predominant, followed by non-typhoidal Salmonella (NTS) (4.55%) and Vibrio parahaemolyticus (4.17%). Notably, enteroaggregative E. coli (35.65%) was the predominant type of DEC identified in this study. The detection rates of viral pathogens were higher in winter and spring. Rotavirus was mainly identified in cases under 5 years of age, while norovirus was more common in cases aged 18-40 years old. Bacterial pathogens were mainly identified in cases aged 18-40 years old in summer. Estimated by the model, the average annual number of infectious diarrhea cases in Beijing from 2015 to 2019 was approximately 68,054 (95%CI: 49,917-104,149). While the model result indicates the presence of significant hidden burden, but are constrained by inherent limitations in the modeling approach and monitoring design. Conclusion:Diarrhea remains a serious public health problem in Beijing, China. Norovirus, DEC, and rotavirus were the predominant pathogens among diarrhea outpatients in Beijing. Continuous surveillance is necessary for guiding prevention and control strategies.

Background:Streptococcus parasuis is a bacterial species recently reclassified from Streptococcus suis. It has been isolated from pigs and cattle, where it may cause various infections. Human infections caused by S. parasuis are rare, with fewer than five publications reported human clinical case to date, and current knowledge regarding its pathogenic potential, antibiotic resistance, and evolutionary context in humans is limited. Results:In this study, the S. parasuis strain S62 was isolated from the blood of a febrile patient. Whole-genome sequencing revealed a genome of 1.93 Mb with a G+C content of 39.5%. Phylogenetic and ANI analyses confirmed that S62 belongs to S. parasuis and is closely related to strains 7500, 221006, NN1, and BS26. The genome harbors virulence-associated genes, including hasC, and putative antibiotic resistance determinants such as a vanY-like glycopeptide resistance gene and the patA-patB efflux system. Phenotypic antimicrobial susceptibility testing showed that S62 was sensitive to most tested antibiotics, with intermediate susceptibility observed only for tetracycline and clindamycin. Functional annotation highlighted the strain's metabolic versatility and potential for environmental adaptation. Conclusion:This study provides a detailed genomic characterization of a human clinical S. parasuis isolate, shedding light on its virulence potential, resistance determinants, and evolutionary relationships. These findings provide a baseline for further investigation and monitoring of S. parasuis in human infections.

OBJECTIVES:This study aimed to investigate the prevalence of diarrhoeagenic Escherichia coli (DEC) among outpatients in Beijing, and to analyse the antimicrobial susceptibility profiles and antimicrobial resistance gene characteristics of the isolated strains. METHODS:From 2021 to 2024, DEC strains were collected from outpatient specimens. After isolation and identification, the minimum inhibitory concentration (MIC) method was used to assess their susceptibility to 16 antibiotics. Whole-genome sequencing was conducted for further analysis. RESULTS:Among the 1209 DEC strains, the highest resistance rates were observed for ampicillin (63.28%) and tetracycline (45.57%). In contrast, significantly lower rates were found for tigecycline (0.41%), amikacin (0.66%), meropenem (3.97%), ertapenem (6.70%), ceftazidime (7.20%), and ciprofloxacin (9.26%). The 0-5 age group demonstrated higher resistance rates to most antibiotics compared with other age groups. Multi-locus sequence typing revealed significant genetic diversity among all strains, with the predominant sequence types identified as ST10 (5.96%), ST1491 (5.21%), ST4 (4.22%), and ST48 (3.47%). Among 111 fluoroquinolone-resistant strains, chromosomal mutations in gyrA and parC genes were predominant (56.76%). Among 612 cephalosporin-resistant isolates, the blaCTX-M gene was the most prevalent resistance gene (30.72%). CONCLUSIONS:DEC infections and the spread of resistance genes pose a significant health threat, especially in children. Consequently, there is an urgent need to enhance the surveillance and research of resistance genes and to promote the rational use of antibiotics.

Other Infectious Diarrheal Diseases (OIDD), caused by pathogens excluding Vibrio cholerae, Shigella, Salmonella typhi, and Salmonella paratyphi, remain a significant public health concern in China. Beijing, a megacity with high population density, extensive mobility, and a temperate monsoon climate, is a prototypical example of temperate monsoon megacities globally. Long-term OIDD patterns, spatiotemporal distribution, and future trends in such dense urban settings are poorly understood, and insights from Beijing can provide valuable guidance for similar cities worldwide. We retrieved case data on OIDD reported in Beijing during 2004-2024 from the Chinese Disease Prevention and Control Information System. Descriptive epidemiology, spatial autocorrelation analysis, hotspot analysis, and the Seasonal Autoregressive Integrated Moving Average (SARIMA) model were employed to investigate the temporal, demographic and regional distribution patterns, identify high-risk regions, and forecast the incidence of OIDD for 2025. A total of 756,933 OIDD cases were reported over the 21-year period. Incidence exhibited an overall downward trend from 2006 to 2022, followed by a rebound from 2023 to 2024. Seasonal peaks occurred in summer (July-August) and winter (December-January), with a notable shift of the summer peak to April-May in 2023. The under-1 year age group showed the highest average annual incidence rate (3502.75 per 100,000), and males were more affected than females (male-to-female ratio 1.19:1). Spatial analysis revealed significant clustering (Moran’s I = 0.18-0.44, P < 0.01), with high-high clusters shifting from central urban districts to suburban areas over time, while persistent low-low clusters were observed in remote districts. The SARIMA (1,1,1) (1,1,1) ₁₂ model accurately predicted monthly cases in 2024 (MAPE = 17.46

OBJECTIVES:Schools are high-risk settings for influenza transmission. During the 2025-26 Northern Hemisphere season, influenza A(H3N2) subclade K (J.2.4.1) rapidly emerged and became predominant, but vaccine effectiveness (VE) in school-associated outbreaks remains unclear. METHODS:We conducted a field investigation of 93 school-associated febrile outbreaks in Beijing, China, from September to December 2025. Cases were febrile students with laboratory-confirmed influenza, and afebrile classmates served as controls. VE against laboratory-confirmed symptomatic infection was estimated using mixed-effects logistic regression, adjusting for age, sex, school type, and outbreak-level clustering. RESULTS:A total of 3797 students were included, of whom 788 were laboratory-confirmed febrile cases and 3009 were afebrile classmates. Primary schools accounted for 74.2% of outbreaks. Overall vaccination rate was 54.6%, with 50.6% among cases and 56.1% among controls. Unadjusted VE was 19.6% (95% CI: 5.9-31.3). After adjustment, VE against laboratory-confirmed influenza was 30.0% (95% CI: 17.3-40.7). Sensitivity analyses yielded consistent results. CONCLUSION:Influenza vaccination provided modest protection against symptomatic A(H3N2) infection in school-aged children, even under conditions of high-intensity exposure and antigenic drift. These findings underscore the value of vaccination in outbreak-prone school settings and highlight the importance of ongoing vaccine strain optimization and outbreak-based VE surveillance.

Toxigenic Vibrio cholerae (V. cholerae) was first sensitively and rapidly detected in hospital wastewater in Beijing, China, on 12 June 2025. Viable V. cholerae was successfully isolated from the wastewater sample and identified as the O1 Ogawa serotype. Whole-genome sequencing and comparative genomic analysis revealed that the isolate was closely related to locally circulating strains but clearly distinct from the seventh pandemic lineage, suggesting its link to indigenous transmission chains. In addition, we immediately initiated a comprehensive and multi-source traceback investigation upon detection of this positive signal, integrating clinical, environmental, and epidemiological data. This case highlights the early-warning and situational-awareness value of wastewater surveillance in detecting emerging pathogens and emphasizes its indispensable role in infectious disease prevention and control systems, providing a scientific basis for timely public health decision-making.

Human adenovirus B7 (HAdV-B7) has emerged as an increasingly important respiratory pathogen in recent years. Ten first grade students experienced symptoms of acute respiratory infection at a primary school in Beijing from November 13 to 21, 2024. We investigated the cause of this outbreak. In partnership with the local center for disease prevention and control, we collected demographic information (age and gender) of the affected students and obtained pharyngeal swab specimens from six students. We used multiplex real-time PCR to screen for 22 common respiratory viruses in these samples. To isolate HAdV, Hep-2 cells were inoculated with HAdV-positive pharyngeal swab samples. Isolates were sequenced by Sanger and whole-genome sequencing. In addition, four HAdV-B7 strains isolated from 2024 to 2025 influenza-like illness surveillance cases were also sequenced as a control to determine whether the same mutations existed. The strains were characterized molecularly using gene homology analysis, recombination analysis and phylogenetic reconstruction. We collected six pharyngeal swab samples from ten students based on consent. All samples were HAdV-positive as determined by multiplex real-time PCR. None of the students were co-infected with other viruses. We successfully isolated the HAdV strain from each student sample. Blast analysis and phylogenetic analysis of the hexon, penton, and fiber genes suggested that this outbreak was caused by HAdV-B7 (P7H7F7). A unique T335S mutation was identified within the RGD loop of the penton base in this outbreak. Whole-genome sequencing confirmed high sequence identity between our isolates and HAdV-B7 strains from multiple regions in China and abroad. In addition, all strains obtained in this outbreak had 57 nucleotides deletion in the E3 region. Interestingly, the same deletion mutants were also found in HAdV-B7 strains isolated from 2024 to 2025 influenza-like illness surveillance cases, indicating that this deletion mutation has been prevalent and may represent an established molecular signature of a circulating HAdV-B7 sublineage. We report the first detection of a human adenovirus type 7 deletion mutant associated with an outbreak of acute respiratory infections in Beijing in 2024. This deletion mutation was prevalent and may represent an established molecular signature of a circulating HAdV-B7 sublineage. How this mutation affects viral pathogenicity remains unclear and needs further investigation. Our findings underscore the critical importance of implementing timely molecular surveillance for guiding outbreak control and informing prevention strategies against respiratory pathogens.

During the early 2025/26 influenza season, influenza A(H3N2) subclade K rapidly predominated in Beijing, China. Using a test-negative design, we estimated influenza vaccine effectiveness (VE) among influenza-like illness outpatients tested between September and December 2025. Among 9,579 participants, sequencing of 316 randomly selected A(H3N2)-positive samples showed 84.8% were subclade K, and antigenic analysis of 65 viruses indicated antigenic divergence. Despite this, adjusted VE against laboratory-confirmed influenza was 41.3% (95% CI: 29.2 to 51.3), indicating moderate protection during this subclade K-dominated season.

BACKGROUND:In the 2024-2025 season, influenza activity returned to pre-COVID-19 pandemic levels, with A(H1N1)pdm09 as the predominant subtype. Reassessment vaccine effectiveness (VE) in hospitalized patients is critical to inform potential adjustments to vaccination policy. METHODS:Using a test-negative design, we evaluated the VE of the seasonal influenza vaccine during the 2024-2025 season against A(H1N1)pdm09-associated hospitalizations with severe acute respiratory infections (SARI) in Beijing, China, from December 9, 2024 to February 9, 2025. VE was estimated by comparing the odds of influenza vaccination between case-patients (those testing positive for A(H1N1)pdm09) and controls (influenza test-negative patients), applying inverse-propensity-to-be-vaccinated weights. RESULTS:The analysis included 1608 hospitalized SARI patients (17.4% tested positive for A(H1N1)pdm09; 13.8% were vaccinated overall). The adjusted VE against A(H1N1)pdm09-associated hospitalizations was 18.8% (95% CI: 0.9% to 33.6%) overall. Specifically, the VE was 45.4% (95% CI: 10.0% to 67.1%) in children aged 0.5-17 years, 43.8% (95% CI: -20.8% to 76.1%) in adults aged 18-59 years, and 8.6% (95% CI: -15.8% to 27.9%) in older adults ≥ 60 years. Among individuals with chronic conditions, the VE was 18.5% (95% CI: -2.3% to 35.2%) and was higher among those with chronic respiratory conditions (40.6%, 95% CI: -1.7% to 65.7%). CONCLUSIONS:During the 2024-2025 season in Beijing, the overall VE against A(H1N1)pdm09-associated SARI hospitalizations was suboptimal. However, moderate VE was observed among children and younger adults, while limited effectiveness was seen in the elderly. Optimizing influenza vaccination strategies, including the introduction of high-dose or adjuvanted vaccines to enhance immune response in older adults, is crucial to alleviate influenza-associated hospitalizations.

We estimated early influenza vaccine effectiveness (VE) for the 2024/25 season in outpatients, in Beijing using a test-negative design. A(H1N1)pdm09 dominated (99.3%), all sequenced strains (n = 38) clustered in clade 6B.1A.5a.2a, and 37 of 38 antigenically similar to the vaccine strain. VE against any influenza virus infection was 48.5% (95% CI: 34.8–59.5) and 48.7% (95% CI: 35.1–59.7) against A(H1N1)pdm09. Vaccination in the current or previous season against any influenza showed a VE of 52.5% to 54.9%, compared to no vaccination in both seasons.

ObjectiveTo establish an adjusted Serfling regression model to estimate the excess cases and the excess epidemic period of hand-foot-mouth disease (HFMD) in Beijing from 2011 to 2019, so as to provide data support and decision-making basis for HFMD prevention and control.MethodsThe weekly number of HFMD cases in Beijing from 2011 to 2019 was utilized for adjusted the Serfling regression model. Then the adjusted model was used to fit the baseline and epidemic threshold of HFMD in Beijing from 2011 to 2019, calculating the excess cases and determining the excess epidemic period.ResultsA total of 279 306 cases of HFMD were reported in Beijing from 2011 to 2019, with the climax of the disease occurring in summer and autumn. After adjusting the fitting R2 of the Serfling regression model to 0.773, a total of 10 excess epidemic periods totaling 92 weeks were estimated, mainly occurring in summer. The highest number of excess cases during an excess epidemic period was found in 2014 (1 272 cases, 95%CI: 990‒1 554), accounting for 65.04% of the actual cases (95%CI: 50.62%‒79.46%).ConclusionThe adjusted Serfling regression model fits well and can be utilized for early warning of HFMD and estimating the disease burden caused by HFMD.