Association of Ambient Temperature and Relative Humidity With Respiratory Syncytial Virus Infections Among Hospitalized Children in Suzhou, Eastern China: A Time-Series Analysis.

Respiratory syncytial virus (RSV) is the leading cause of clinical pneumonia in children. We aimed to investigate the associations between ambient temperature, relative humidity, and pediatric RSV infections, and to assess the disease burden attributable to cold or humid conditions. Daily data on RSV hospitalizations among children aged ≤5 years, mean temperature, and relative humidity in Suzhou, China, from January 2016 to December 2019 were collected. A distributed lag nonlinear model with quasi-Poisson regression was employed to assess the exposure-lag-response associations. Attributable risks were calculated to quantify the disease burden due to climatic factors. We found an inverted U-shaped relationship between temperature and RSV infections, with the cumulative risk of RSV peaking at 7.5°C (RR = 4.30, 95% CI: 3.08-6.02). The exposure-response curves for relative humidity exhibited a generally positive trend, peaking at 100.0% (RR = 3.14, 95% CI: 1.84-5.34). Using median values as references, the highest risk effects of extremely low (RR = 1.14, 95% CI: 1.04-1.25) and low (RR = 1.22, 95% CI: 1.12-1.32) temperatures, as well as high (RR = 1.09, 95% CI: 1.04-1.13) and extremely high (RR = 1.16, 95% CI: 1.07-1.27) relative humidity, occurred on the day of exposure and persisted for extended periods. The attributable fraction of RSV infections associated with cold or humid conditions was 55.23% (95% CI: 50.01%-64.03%) and 12.02% (95% CI: 9.36%-20.24%), respectively. The risk effect of high relative humidity was stronger in children aged 1-5 years. Our findings suggest nonlinear, lagged associations between climatic factors and pediatric RSV infections, which may inform future healthcare planning and RSV immunization strategies.