BACKGROUND:Dengue is known to be associated with El Niño-Southern Oscillation (ENSO) but the size of the effect is unclear, as is the influence of anthropogenic climate change (ACC). We aimed to quantify the associations between ENSO and dengue risk in 21 countries, and to estimate the contribution of ACC to the ENSO-related dengue burden. METHODS:We collected monthly dengue cases and observed and simulated climate data from 21 countries including 1237 locations from 2000 to 2019. We characterised Eastern Pacific (EP) and Central Pacific (CP) ENSO exposures for each location based on the E and C indices and their respective teleconnections. Location-specific association between ENSO exposure and dengue cases was estimated using negative binomial generalised linear model combined with best linear unbiased predictions. We also estimated the ENSO-related dengue burden under scenarios with and without ACC. FINDINGS:For each standard deviation increase in EP-El Niño strength and CP-La Niña strength, the overall risk of dengue cases across locations changed by 23·70% (95% CI 21·50 to 25·94) and -9·07% (-9·91 to -8·21), respectively. During 2000 to 2019, 4·45% (95% empirical CI [eCI] 3·75 to 5·32) and -3·34% (-4·01 to -2·64) of dengue cases were attributable to EP-El Niño strength and CP-La Niña strength, respectively. ACC accounted for 48·64% (95% eCI 38·01 to 60·19) of the EP-El Niño-attributable dengue increment and 33·05% (28·66 to 38·25) of the CP-La Niña-attributable reduction. These estimates corresponded to 403 197 (95% eCI 315 109 to 498 940) and -205 641 (-238 030 to -178 329) dengue cases across 1237 locations, respectively. The associations with ENSO varied strongly across the 21 countries. INTERPRETATION:This study presents new model-based evidence of the strong associations between ENSO and dengue risk at a multicountry level, and suggests that the contribution of ACC to the effects of ENSO might differ geographically. FUNDING:Prevention and Control of Emerging and Major Infectious Diseases National Science and Technology Major Project, the National Natural Science Foundation of China, and the Czech Ministry of Education Youth and Sport's programme ERC CZ.

BackgroundInfectious diarrhea remains a significant public health challenge, with climatic factors potentially playing a crucial role in its epidemiological spread. However, the precise mechanisms through which the El Niño-Southern Oscillation (ENSO) influences diarrheal morbidity are still not fully understood.MethodsWe collected monthly other infectious diarrhea (OID) incidence and climatic data across the 31 provincial administrative divisions of mainland China (2005–2019). Wavelet analysis was employed to examine the periodicity of OID and the phase relationships between ENSO, climate factors and OID. Generalized additive models (GAM) and Peter and Clark Momentary Conditional Independence (PCMCI) algorithm were used to quantify exposure-response relationship and establish causal pathways in China.ResultsFrom 2005 to 2019, a total of 13,620,167 OID cases were reported in 31 provincial regions of China, with the highest incidence of OID concentrated in the southern and eastern regions of China. Wavelet analysis identified a significant periodicity between ENSO cycles and diarrhea incidence patterns, demonstrating that La Niña events (characterized by low ENSO index) were associated with subsequent increases in incidence with a 6-month lag. The exposure-response relationship showed an inverted J-shaped curve in North and East China, while a nearly linear relationship was observed in Northeast, Central, Southwest and Northwest China. PCMCI analysis elucidated that precipitation is an indirect link between ENSO and OID.ConclusionOur study suggests that a low ENSO index (La Niña) may drive the incidence of OID in China. The findings provide a scientific basis for predicting and warning of OID based on ENSO.

Urban greenness is celebrated for its environmental and health benefits, yet its association with ozone (O-3)-related health risk via biogenic volatile organic compound (BVOC) emissions remains underexplored. Integrating WRF-CMAQ model simulations and population-based epidemiological analyses using a case time-series study design, we examined the paradoxical link between greenness and O-3 formation and associated mortality risk in Zhejiang, China, from 2013 to 2020. The association between per IQR increase in O-3 and all-cause mortality risk was significantly stronger in subdistricts with a high greenness exposure level (mortality increase in 4.8%, 95% CI: 3.8-5.7) compared to subdistricts with a low greenness exposure level (1.0%, 95% CI: 0.2-1.7; P for difference < 0.001). This observational association is supported by the WRF-CMAQ model simulations, which estimated a median greenness contribution to O-3 formation of 13.76% (IQR: 5.68%) in summer and 1.16% (0.85%) in winter. Similar difference in mortality risk was also observed for cardiovascular mortality and respiratory mortality. This effect modification was consistent across age and sex subgroups and more pronounced during the cold season and in rural areas. By highlighting the counterintuitive role of greenness in O-3-related health risks, our study offers critical insights for urban greening, emphasizing the need to balance ecological ambitions with public health imperatives for a sustainable environment.

Introduction To quantify the impact of tropical cyclones on dengue transmission dynamics and related disease burden by integrating field entomology with dynamic modelling in Guangzhou, China.Methods Guangzhou was selected as the study site considering that it is China’s most dengue-endemic coastal megacity with frequent tropical cyclones and the country’s largest recorded dengue outbreak in 2014. Mark–release–recapture experiments with laboratory simulations were performed in 2024 to assess the flight distance, reproduction and survival of Aedes albopictus under cyclone and baseline conditions to estimate human–mosquito contact rates. These data informed a dynamic susceptible–incubation–infected–recovered model simulating the 2014 dengue epidemic during Typhoons Rammasun and Kalmaegi. We estimated excess cases and economic losses against counterfactual baselines and projected the impact of enhanced vector control.Results During cyclones, Aedes albopictus maximum flight distance increased by 63.0% and human–mosquito contact rate by 30.1%. Estimated R0 increased from 1.10 (baseline) to 1.43 (Rammasun) and 1.29 (Kalmaegi). The estimated excess burden reached 217 excess cases (US$76 400) for Rammasun and 5131 cases (US$1.93 million) for Kalmaegi. Enhanced vector control during Kalmaegi was projected to avert 59 360 additional cases (US$20.91 million).Conclusions Tropical cyclones amplify dengue transmission by expanding mosquito dispersal and intensifying human–vector contact. Early vector control, guided by warnings, substantially reduces cases and costs.

Background Dengue risk is increasingly shaped by climate change and rapid urbanization, yet comprehensive, multidimensional risk assessments grounded in a One Health perspective remain scare.Methods We develop a geographically eXplainable artificial intelligence (GeoXAI) model to estimate dengue hazard across China in 2024 (current), 2050, and 2100 under different shared socioeconomic pathway (SSP) scenarios. A hazard-exposure-vulnerability framework is then used to assess dengue risk by integrating dengue hazard, human exposure, and social vulnerability.Results Here we show a northward expansion of high-hazard areas, with the minimum temperature in the coldest month being the dominant driver (27.2% contribution). Moreover, socioeconomic factors such as population density (3.8%) and urbanization level (2.7%) will further amplify dengue hazard. Current dengue risk assessments reveal high-risk clusters in Southwest China and megacities. Dengue risk exhibits spatially heterogeneous escalation in the future, with Southwest and Southeast China facing the steepest growth and Northwest China experiencing disproportionate increases. Compared to the current, dengue risk in SSP585-a high greenhouse gas emission scenario and limited climate policy interventions-increases by 6.01% (2050) and 8.21% (2100), representing the largest escalation among the three SSPs.Conclusions Despite ongoing disease control efforts, our findings underscore the need to intensify integrated surveillance and multidimensional intervention strategies against escalating dengue risk in China, and offers lessons for other prevalent Aedes-borne diseases (e.g., chikungunya).

Multidimensional impacts of human settlement environment (HSE) on childhood diarrhea in low- and middle-income countries (LMICs) remain largely underexplored. Diarrhea data used in this study were collected from the Demographic and Health Surveys Program during 2005-2019. For each location, 65 HSE-related indicators were measured from land-cover product, gridded socioeconomic dataset and other sources, and then classified into five dimensions: living environment, socioeconomic condition, public service, climatic moderation, and landscape ecology. Confirmatory factor analysis was used to construct the dimensions of HSE. Binomial generalized linear mixed-effects models were employed to explore the association between HSE dimensions and risk of childhood diarrhea. A total of 1,340,334 children under five from 53 LMICs were included in this study. All the five dimensions, except for landscape ecology, were negatively associated with childhood diarrhea. For example, compared with the low level, high level of socioeconomic condition was linked to a lower diarrhea risk (OR = 0.671, 95 % CI: 0.643-0.701). Regionally, these associations were particularly evident in Africa and Asia. Stratified analysis revealed that the impacts of living environment and socioeconomic condition dimensions were more pronounced in urban, wealthy, and high-education households, while public service had greater effects in rural, low-income settings. In conclusion, well-planned settlement environments, higher socioeconomic status, high-quality public services, and suitable climatic conditions are associated with mitigated risk of childhood diarrhea. These findings provide valuable insights for developing context-specific interventions.

Norovirus (NoV) represents a major cause of acute diarrhea among children under 5 years old in China, yet its overall disease burden is frequently underestimated in systematic reporting. This meta-analysis aimed to provide a comprehensive assessment of the burden of NoV-related diarrhea in Chinese children under 5 years of age based on published literature between 2020 and 2024. We conducted a systematic search across PubMed, Web of Science, CNKI, and WanFang Data, identifying 60 eligible studies. The quality of these studies was assessed using the STROBE checklist. Heterogeneity was evaluated through Cochran’s Q test and the I² statistic, while publication bias was examined using Egger’s test and funnel plots. Pooled positivity rates were analyzed employing a random-effects model. All analyses were done at 95

Objectives Although the relationship between urbanization and influenza has received increasing attention, previous studies have often examined this relationship based on single indicators, neglecting the multi-dimensions of urban development and their integrated impact on influenza incidence in neighboring cities. Methods A multidimensional urbanization evaluation framework was developed based on social, economic, and ecological dimensions to comprehensively assess urbanization. Then, we analyzed the impact of urbanization development on influenza incidence within and across cities using Bayesian spatiotemporal models and spatial Durbin models. Regional heterogeneity analysis was performed to investigate the impact of urbanization on influenza incidence within cities. Results From 2014 to 2019, there were 5,062,254 influenza cases in 283 prefecture-level cities in China. Each standard deviation increment in comprehensive, social, and economic indexes of urbanization was associated with a 14.9% (95% CI: 6.1%, 24.3%), 9.9% (95% CI: 3.5%, 16.3%), and 13.4% (95% CI: 4.5%, 23.7%) increase in influenza incidence, respectively. The effects of urban development on influenza incidence varied significantly across regions, with the greatest impact found in southern China. Additionally, a significant positive spatial spillover effect of urbanization was observed on influenza incidence in surrounding cities. Conclusions Urbanization and its various dimensions were linked to increased risk of local influenza incidence, which also showed substantial positive spatial spillover effect to surrounding areas. During the rapid urbanization process in China, local governments should prioritize equity and accessibility in healthcare services and strengthen the coordinated prevention and control of influenza epidemics across cities.

BACKGROUND:Exposure to fine particles (PM2.5) from wildfires is known to cause deaths and chronic diseases, but its effect on respiratory infections, especially in children and adolescents, is not well characterized. We aimed to comprehensively assess the association between short-term exposure to wildfire-related PM2.5 and the incidence and mortality of respiratory transmitted diseases in children and adolescents. METHODS AND FINDINGS:Data on daily counts of incident and mortality cases of respiratory transmitted diseases in persons aged 4-24 years old were collected from China Information System for Disease Control and Prevention, covering 501 cities from 2008 to 2019. Daily concentrations of wildfire-related PM2.5 were estimated using machine learning and chemical transport models at a 0.25°×0.25° spatial resolution. We used time-stratified case-crossover design with conditional logistic regression to estimate the association between short-term exposures to wildfire-related PM2.5 and incidence and mortality of respiratory transmitted diseases, adjusting for temperature, relative humidity, precipitation, and total PM2.5. There were 6,089,271 incident cases and 1,034 mortality cases of 10 respiratory transmitted diseases included in our analyses. Each 5 μg/m3 increase in the lag 0-28-day (average of current day and previous 28 days) for wildfire-related PM2.5 was associated with a 6.8% (95%CI: 5.0%, 8.7%) increase in the daily incidence rate of respiratory transmitted diseases, which is greater than that of a 1.2% (1.0%, 1.4%) increase associated with the same increase of non-wildfire-related PM2.5. A 5 μg/m3 increase in wildfire-related PM2.5 was associated with a 28.6% (21.0%, 36.8%), 5.2% (2.3%, 8.3%), 12.6% (9.5%, 15.8%), and 13.6% (5.6%, 22.2%) increase in the incidence of seasonal influenza, scarlet fever, rubella, and measles, respectively. Although wildfire-related PM2.5 constitutes only 2.7% of the total PM2.5, it contributes significantly to respiratory transmitted diseases, accounting for 10.8% of all PM2.5-associated cases. In areas where the annual concentration of wildfire-related PM2.5 is lower than 1.5 μg/m3, the proportion of cases associated with wildfire-related PM2.5 reached 29.7%. Study limitations include potential exposure misclassification from using city-average wildfire PM2.5 as a proxy for individual exposure and an inability to adjust for some potential confounders. CONCLUSIONS:Short-term exposure to wildfire-related PM2.5 was associated with increased incidence of respiratory transmitted diseases, surpassing the impact observed with non-wildfire-related PM2.5. This phenomenon is not restricted to regions with high pollutant concentrations; even populations residing in areas with lower concentrations of wildfire-related PM2.5 are at an increased risk of these respiratory conditions. Consequently, there emerges a pressing global imperative to confront the escalating challenges presented by climate change and the intensifying menace of wildfires.

BACKGROUND:The relationship between ambient temperature and infectious disease incidence lacks comprehensive documentation. Our study, therefore, sought to systematically determine the national association between temperature and the incidence of infectious diseases, categorized into respiratory, gastrointestinal and enterovirus, and vector-borne categories. We aimed to study the association between extreme cold and heat extreme temperature on infectious disease occurrence among children and teenagers, and to evaluate the secular trends in these diseases in relation to temperature extremes. METHODS:We accessed the dataset encompassing 8,731,930 cases of 27 distinct infectious diseases, spanning respiratory, gastrointestinal and enterovirus infections, and vector-borne categories, across 507 Chinese cities from 2008 to 2019. Employing a time-stratified case-crossover design, we quantified the association between temperature exposure and the risk of infectious diseases specific to each city. The attributable fractions for temperature-related risks were determined by identifying extreme temperatures exceeding the 90th percentile and falling below the 10th percentile of the respective city-specific temperature distributions, indicative of heat and cold effects. A comparative analysis of these attributable fractions between the periods 2008-2010 and 2017-2019 was conducted to evaluate the secular changes of infectious diseases associated with cold and heat. FINDINGS:Our analysis revealed significant non-linear associations between temperature and the incidence of specific infectious diseases. Cold temperatures were found to be responsible for 1.35% (95% CI: 1.18 to 1.51%) of respiratory infectious disease cases. In contrast, heat was attributed to a lower proportion, with 0.29% (95% CI: 0.25 to 0.33%) of such cases. Among gastrointestinal and enterovirus diseases, a more substantial 4.93% (95% CI: 4.82 to 5.04%) of cases were linked to heat exposure. Notably, vector-borne diseases demonstrated the highest attributable fraction to heat, with 22.12% (95% CI: 21.82 to 22.41%) of cases affected. Specifically, five diseases-scarlet fever, tuberculosis, mumps, leprosy, and typhus-exhibited an increased incidence associated with cold temperatures. Notably, for scarlet fever, leprosy, and typhus, the attributable fraction escalated from the period 2008-2010 to 2017-2019. However, findings for leprosy should be interpreted with caution due to its low incidence. As for heat-related diseases, thirteen were identified, with the attributable fraction for nine diseases-tuberculosis, pertussis, hand, foot, and mouth disease, infectious diarrhea, dysentery, hepatitis A, typhoid and paratyphoid, dengue, and Japanese encephalitis-showing a marked increase over the same comparative timeframes. INTERPRETATION:The temperature increase observed from 2008-2010 to 2017-2019 has been accompanied by a rising trend in heat-related infections. Among all infectious diseases in Chinese children and adolescents, more than half (13 out of 24) are heat-related, compared to five infections linked to extreme cold. The risk of gastrointestinal and enterovirus infections was associated with extreme hot temperatures, with vector-borne diseases particularly responsive to extreme heat. These findings highlight an urgent requirement for proactive public health measures to address the potential impact of temperature variability on infectious disease outbreaks, safeguarding vulnerable demographics in the context of climate change.

Background: Studies have reported the adverse effects of cold events on influenza. However, the role of critical factors, such as characteristics of cold spells, and regional variations remain unresolved. Objective: We aimed to systematically evaluate the association between cold spells and influenza incidence in mainlandChina. Methods: This time series analysis used surveillance data of daily influenza from 325 sites in China in the 2014-2019 period.A total of 15 definitions of cold spells were adopted based on combinations of temperature thresholds and days of duration. A distributed lag linear model was used to estimate the short-term effects of cold spells on influenza incidence during the cool seasons (November to March), and we further explored the potential impact of cold spell characteristics (ie, intensity, duration, and timing during the season) on the estimated associations. Meta-regressions were used to evaluate the modification effect of city-level socioeconomic indicators. Results: The overall effect of cold spells on influenza incidence increased with the temperature threshold used to define cold spells, whereas the added effects were generally small and not statistically significant. The relative risk of influenza-associated with cold spells was 3.35 (95% CI 2.89-3.88), and the estimated effects were stronger during the middle period of cool seasons. The health effects of cold spells varied geographically and residents in Jiangnan region were vulnerable groups(relative risk 7.36, 95% CI 5.44-9.95). The overall effects of cold spells were positively correlated with the urban population density, population size, gross domestic product per capita, and urbanization rate, indicating a sterner response to cold spells in metropolises. Conclusions: Cold spells create a substantial health burden on seasonal influenza in China. Findings on regional and socioeconomic differences in the health effects of cold spells on seasonal influenza may be useful in formulating region-specific public health policies to address the hazardous effects of cold spells.

Background: Beyond the direct effect of COVID-19 infection on young people, the wider impact of the pandemic on otherinfectious diseases remains unknown. Objective: This study aims to assess changes in the incidence and mortality of 42 notifiable infectious diseases during thepandemic among children and adolescents in China, compared with prepandemic levels. Methods: The Notifiable Infectious Disease Surveillance System of China was used to detect new cases and fatalities amongindividuals aged 5-22 years across 42 notifiable infectious diseases spanning from 2018 to 2021. These infectious diseases werecategorized into 5 groups: respiratory, gastrointestinal and enterovirus, sexually transmitted and blood-borne, zoonotic, andvector-borne diseases. Each year (2018-2021) was segmented into 4 phases: phase 1 (January 1-22), phase 2 (January 23-April7), phase 3 (April 8-August 31), and phase 4 (September 1-December 31) according to the varying intensities of pandemicrestrictive measures in 2020. Generalized linear models were applied to assess the change in the incidence and mortality withineach disease category, using 2018 and 2019 as the reference. Results: A total of 4,898,260 incident cases and 3701 deaths were included. The overall incidence of notifiable infectiousdiseases decreased sharply during the first year of the COVID-19 pandemic (2020) compared with prepandemic levels (2018 and2019), and then rebounded in 2021, particularly in South China. Across the past 4 years, the number of deaths steadily decreased.The incidence of diseases rebounded differentially by the pandemic phase. For instance, although seasonal influenza dominatedrespiratory diseases in 2019, it showed a substantial decline during the pandemic (percent change in phase 2 2020: 0.21, 95% CI0.09-0.50), which persisted until 2021 (percent change in phase 4 2021: 1.02, 95% CI 0.74-1.41). The incidence of gastrointestinal and enterovirus diseases decreased by 33.6% during 2020 but rebounded by 56.9% in 2021, mainly driven by hand, foot, andmouth disease (percent change in phase 3 2021: 1.28, 95% CI 1.17-1.41) and infectious diarrhea (percent change in phase 3 2020:1.22, 95% CI 1.17-1.28). Sexually transmitted and blood-borne diseases were restrained during the first year of 2021 but reboundedquickly in 2021, mainly driven by syphilis (percent change in phase 3 2020: 1.31, 95% CI 1.23-1.40) and gonorrhea (percentchange in phase 3 2020: 1.10, 95% CI 1.05-1.16). Zoonotic diseases were not dampened by the pandemic but continued to increaseacross the study period, mainly due to brucellosis (percent change in phase 2 2020: 0.94, 95% CI 0.75-1.16). Vector-borne diseasesshowed a continuous decline during 2020, dominated by hemorrhagic fever (percent change in phase 2 2020: 0.68, 95% CI0.53-0.87), but rebounded in 2021.Conclusions: The COVID-19 pandemic was associated with a marked decline in notifiable infectious diseases in Chinesechildren and adolescents. These effects were not sustained, with evidence of a rebound to prepandemic levels by late 2021. Toeffectively address the postpandemic resurgence of infectious diseases in children and adolescents, it will be essential to maintaindisease surveillance and strengthen the implementation of various initiatives. These include extending immunization programs,prioritizing the management of sexually transmitted infections, continuing feasible nonpharmaceutical intervention projects, andeffectively managing imported infections

This study assesses the association of short-term exposure to PM2.5 (particles <= 2.5 mu m) on infectious diseases among Chinese children and adolescents. Analyzing data from 507 cities (2008-2021) on 42 diseases, it focuses on PM2.5 components (black carbon (BC), ammonium (NH4+), inorganic nitrate (NO3-), organic matter (OM), and sulfate (SO42-)). PM2.5 constituents significantly associated with incidence. Sulfate showed the most substantial effect, increasing all-cause infectious disease risk by 2.72 % per interquartile range (IQR) increase. It was followed by BC (2.04 % increase), OM (1.70 %), NO3- (1.67 %), and NH4+ (0.79 %). Specifically, sulfate and BC had pronounced impacts on respiratory diseases, with sulfate linked to a 10.73 % increase in seasonal influenza risk and NO3- to a 16.39 % rise in tuberculosis. Exposure to PM2.5 also marginally increased risks for gastrointestinal, enterovirus, and vectorborne diseases like dengue (7.46 % increase with SO42-). Sexually transmitted and bloodborne diseases saw an approximate 6.26 % increase in incidence, with specific constituents linked to diseases like hepatitis C and syphilis. The study concludes that managing PM2.5 levels could substantially reduce infectious disease incidence, particularly in China's middle-northern regions. It highlights the necessity of stringent air quality standards and targeted disease prevention, aligning PM2.5 management with international guidelines for public health protection.

BackgroundBeyond the direct effect of COVID-19 infection on young people, the wider impact of the pandemic on other infectious diseases remains unknown. ObjectiveThis study aims to assess changes in the incidence and mortality of 42 notifiable infectious diseases during the pandemic among children and adolescents in China, compared with prepandemic levels. MethodsThe Notifiable Infectious Disease Surveillance System of China was used to detect new cases and fatalities among individuals aged 5-22 years across 42 notifiable infectious diseases spanning from 2018 to 2021. These infectious diseases were categorized into 5 groups: respiratory, gastrointestinal and enterovirus, sexually transmitted and blood-borne, zoonotic, and vector-borne diseases. Each year (2018-2021) was segmented into 4 phases: phase 1 (January 1-22), phase 2 (January 23-April 7), phase 3 (April 8-August 31), and phase 4 (September 1-December 31) according to the varying intensities of pandemic restrictive measures in 2020. Generalized linear models were applied to assess the change in the incidence and mortality within each disease category, using 2018 and 2019 as the reference. ResultsA total of 4,898,260 incident cases and 3701 deaths were included. The overall incidence of notifiable infectious diseases decreased sharply during the first year of the COVID-19 pandemic (2020) compared with prepandemic levels (2018 and 2019), and then rebounded in 2021, particularly in South China. Across the past 4 years, the number of deaths steadily decreased. The incidence of diseases rebounded differentially by the pandemic phase. For instance, although seasonal influenza dominated respiratory diseases in 2019, it showed a substantial decline during the pandemic (percent change in phase 2 2020: 0.21, 95% CI 0.09-0.50), which persisted until 2021 (percent change in phase 4 2021: 1.02, 95% CI 0.74-1.41). The incidence of gastrointestinal and enterovirus diseases decreased by 33.6% during 2020 but rebounded by 56.9% in 2021, mainly driven by hand, foot, and mouth disease (percent change in phase 3 2021: 1.28, 95% CI 1.17-1.41) and infectious diarrhea (percent change in phase 3 2020: 1.22, 95% CI 1.17-1.28). Sexually transmitted and blood-borne diseases were restrained during the first year of 2021 but rebounded quickly in 2021, mainly driven by syphilis (percent change in phase 3 2020: 1.31, 95% CI 1.23-1.40) and gonorrhea (percent change in phase 3 2020: 1.10, 95% CI 1.05-1.16). Zoonotic diseases were not dampened by the pandemic but continued to increase across the study period, mainly due to brucellosis (percent change in phase 2 2020: 0.94, 95% CI 0.75-1.16). Vector-borne diseases showed a continuous decline during 2020, dominated by hemorrhagic fever (percent change in phase 2 2020: 0.68, 95% CI 0.53-0.87), but rebounded in 2021. ConclusionsThe COVID-19 pandemic was associated with a marked decline in notifiable infectious diseases in Chinese children and adolescents. These effects were not sustained, with evidence of a rebound to prepandemic levels by late 2021. To effectively address the postpandemic resurgence of infectious diseases in children and adolescents, it will be essential to maintain disease surveillance and strengthen the implementation of various initiatives. These include extending immunization programs, prioritizing the management of sexually transmitted infections, continuing feasible nonpharmaceutical intervention projects, and effectively managing imported infections.

Background:Co-existence of efficient transportation networks and geographic imbalance of medical resources greatly facilitated inter-city migration of patients of infectious diseases in China. Methods:To characterize the migration patterns of major notifiable infectious diseases (NIDs) during 2016-2020 in China, we collected migratory cases, who had illness onset in one city but were diagnosed and reported in another, from the National Notifiable Infectious Disease Reporting System, and conducted a nationwide network analysis of migratory cases of major NIDs at the city (prefecture) level. Findings:In total, 2,674,892 migratory cases of NIDs were reported in China during 2016-2020. The top five diseases with the most migratory cases were hepatitis B, tuberculosis, hand, foot and mouth disease (HFMD), syphilis, and influenza, accounting for 79% of all migratory cases. The top five diseases with the highest proportions of migratory cases were all zoonotic or vector-borne (37.89%‒99.98%). The network analysis on 14 major diseases identified three distinct migration patterns, where provincial capitals acted as key node cities: short distance (e.g., pertussis), long distance (e.g., HIV/AIDS), and mixed (e.g., HFMD). Strong drivers for patient migration include population mobility and labor flow intensities between cities as well as the economic development level of the destination city. Interpretation:Collaborative prevention and control strategies should target cities experiencing frequent patient migration and cater to unique migration patterns of each disease. Addressing disparity in healthcare accessibility can also help alleviate case migration and thereby reduce cross-regional transmission. Funding:National Key Research and Development Program of China.

This study aims to examine the association between temperature variabilit (TV) exposure and influenza incidence in China, and the modification effect of PM 2.5 levels. Data on daily influenza cases, weather conditions, and PM 2.5 concentrations were collected from 339 cities across mainland China from 2014 to 2019. TV was computed as the standard deviation of daily maximum and minimum temperatures for the current day and the previous several days (i.e., TV0-1 to TV0-7). A space-time-stratified case-crossover design with conditional Poisson regression was employed. Overall, each 1 degrees C increase in TV0-6 was linked to 3.3 % (95 % CI: 3.1 %, 3.5 %) rise in influenza incidence, potentially attributing 14.73 % (95 % CI: 14.08 %, 15.37 %) of cases to this exposure. PM 2.5 concentration showed substantial modification effect on the association, such that the relative risk (RR) of influenza incidence grew from 1.027 (95 % CI: 1.025, 1.029) to 1.040 (95 % CI: 1.038, 1.042) as PM 2.5 levels increased from 15 to 75 mu g/m3 . Females and individuals over 65 years old were more susceptible to TV exposure and the PM 2.5 modification. Stronger effects were observed during cold season and in North region. The findings highlight the integrating considerations of TV and PM 2.5 exposures into public health measures for influenza prevention and control.

BackgroundAn accelerated epidemiological transition, spurred by economic development and urbanization, has led to a rapid transformation of the disease spectrum. However, this transition has resulted in a divergent change in the burden of infectious diseases between urban and rural areas. The objective of our study was to evaluate the long-term urban-rural disparities in infectious diseases among children, adolescents, and youths in China, while also examining the specific diseases driving these disparities.Methods and findingsThis observational study examined data on 43 notifiable infectious diseases from 8,442,956 cases from individuals aged 4 to 24 years, with 4,487,043 cases in urban areas and 3,955,913 in rural areas. The data from 2013 to 2021 were obtained from China's Notifiable Infectious Disease Surveillance System. The 43 infectious diseases were categorized into 7 categories: vaccine-preventable, bacterial, gastrointestinal and enterovirus, sexually transmitted and bloodborne, vectorborne, zoonotic, and quarantinable diseases. The calculation of infectious disease incidence was stratified by urban and rural areas. We used the index of incidence rate ratio (IRR), calculated by dividing the urban incidence rate by the rural incidence rate for each disease category, to assess the urban-rural disparity. During the nine-year study period, most notifiable infectious diseases in both urban and rural areas exhibited either a decreased or stable pattern. However, a significant and progressively widening urban-rural disparity in notifiable infectious diseases was observed. Children, adolescents, and youths in urban areas experienced a higher average yearly incidence compared to their rural counterparts, with rates of 439 per 100,000 compared to 211 per 100,000, respectively (IRR: 2.078, 95% CI [2.075, 2.081]; p < 0.001). From 2013 to 2021, this disparity was primarily driven by higher incidences of pertussis (IRR: 1.782, 95% CI [1.705, 1.862]; p < 0.001) and seasonal influenza (IRR: 3.213, 95% CI [3.205, 3.220]; p < 0.001) among vaccine-preventable diseases, tuberculosis (IRR: 1.011, 95% CI [1.006, 1.015]; p < 0.001), and scarlet fever (IRR: 2.942, 95% CI [2.918, 2.966]; p < 0.001) among bacterial diseases, infectious diarrhea (IRR: 1.932, 95% CI [1.924, 1.939]; p < 0.001), and hand, foot, and mouth disease (IRR: 2.501, 95% CI [2.491, 2.510]; p < 0.001) among gastrointestinal and enterovirus diseases, dengue (IRR: 11.952, 95% CI [11.313, 12.628]; p < 0.001) among vectorborne diseases, and 4 sexually transmitted and bloodborne diseases (syphilis: IRR 1.743, 95% CI [1.731, 1.755], p < 0.001; gonorrhea: IRR 2.658, 95% CI [2.635, 2.682], p < 0.001; HIV/AIDS: IRR 2.269, 95% CI [2.239, 2.299], p < 0.001; hepatitis C: IRR 1.540, 95% CI [1.506, 1.575], p < 0.001), but was partially offset by lower incidences of most zoonotic and quarantinable diseases in urban areas (for example, brucellosis among zoonotic: IRR 0.516, 95% CI [0.498, 0.534], p < 0.001; hemorrhagic fever among quarantinable: IRR 0.930, 95% CI [0.881, 0.981], p = 0.008). Additionally, the overall urban-rural disparity was particularly pronounced in the middle (IRR: 1.704, 95% CI [1.699, 1.708]; p < 0.001) and northeastern regions (IRR: 1.713, 95% CI [1.700, 1.726]; p < 0.001) of China. A primary limitation of our study is that the incidence was calculated based on annual average population data without accounting for population mobility.ConclusionsA significant urban-rural disparity in notifiable infectious diseases among children, adolescents, and youths was evident from our study. The burden in urban areas exceeded that in rural areas by more than 2-fold, and this gap appears to be widening, particularly influenced by tuberculosis, scarlet fever, infectious diarrhea, and typhus. These findings underscore the urgent need for interventions to mitigate infectious diseases and address the growing urban-rural disparity.

To investigate the progress of disparities in human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), gonorrhea, and syphilis among children and adolescents aged 6–22 years in China during 2013–2021. A total of 614 325 cases data were extracted from the Chinese Information System for Infectious Diseases Control and Prevention during 2013–2021. Puberty health education data were drew from the Student Health Surveillance in 2021. Disparity patterns and average annual percentage changes (AAPCs) in sexually transmitted infections (STIs) incidence or new cases in China were examined using descriptive statistics and joinpoint regression. The incidence across 345 cities was stratified by gross domestic product (GDP). Between 2013 and 2021, there were 614 325 reported cases of HIV/AIDS, gonorrhea, and syphilis among children and adolescents aged 6–22, with an annual average incidence of 24.0967 per 100 000. The expansion of HIV/AIDS has halted, yet the surge in gonorrhea and syphilis remains notably pronounced. The ratio of male to female AIDS incidence increased from 2.75 (2.60, 2.90) to 7.13 (6.68, 7.62), but that of syphilis changed from 0.33 (0.32, 0.34) to 0.56 (0.55, 0.57). Students and out‐of‐school individuals aged 13–15 experienced a notably high increase in STI cases, surpassing other age groups, with an average annual percentage increase of 29.2% and 26.3%, respectively. Nonstudents consistently had a higher incidence rate than students, with an IRR reaching 31.80 (31.24, 32.37) in 2021. A noticeable clustering pattern of new cases emerged in the southeastern region of the Heihe‐Tengchong line, extending inland from the coastal areas. Districts and counties with lower rates of puberty sexual health education tended to have higher average STI incidence rates. At the prefecture and city levels, there was a noticeable upward trend on average STI incidence rates in cities with per capita GDPs. Strategies to address those disparities include promoting equitable health education, and widespread sexual health education, particularly in areas with limited access to education and experiencing rapid economic development. The effectiveness of sexual health education intervention needs to be further evaluated in well‐designed studies.

Infectious diarrhea imposes substantial disease burden in China, with local climate identified as a key risk factor. In this study, we aimed to explore the association between hydrometeorological conditions and the incidence of infectious diarrhea, and investigate the modification effect of urbanization, which remained unclear previously. Monthly data were collected from 1 January 2021 to 31 December 2022 from each city of mainland China on cases of infectious diarrhea other than cholera, dysentery, typhoid and paratyphoid (i.e. other infectious diarrhea, OID), temperature and precipitation. We used Palmer drought severity index (PDSI) to represent local hydrometeorological conditions (dry and wet). A spatiotemporal Bayesian hierarchical model combined with distributed lag nonlinear model was specified to explore the association between PDSI and the relative risk of OID. The effect size of hydrometeorological conditions at different urbanization levels were quantified through a linear interaction term. A total of 1999 947 OID cases were included. There was a N-shaped cumulative association between PDSI and OID incidence over a maximum lag of 4 months. The effect of extreme dry conditions persisted over lag 1-3 months and peaked at the 2-month lag (RR = 2.67, 95%CI: 2.44-2.91). By contrast, the relative risk of OID increased immediately under extreme wet conditions (RR = 1.97, 95%CI: 1.68-2.32 at lag 0 month). Children and the older population were particularly susceptible to extreme dry and wet conditions, respectively. Areas with lower urbanization rate, healthcare resources and economic levels, and higher population density showed a higher risk of OID related to extreme dry conditions. While the modification effects of these urbanization characteristics were limited for extreme wet conditions. There was a nonlinear and lagged association between hydrometeorological conditions and the incidence of OID in mainland China, which may be modified in diverse patterns by urbanization indicators. Our findings will provide valuable reference for better prevention and control of OID.