Effects of temperature on influenza activity across different populations in a subtropical region: a 7-year surveillance in Changsha, China.

Changsha, a city of 10 million people in China, has complex patterns of influenza activities. There is limited evidence on how temperature influences influenza activity across different populations in a subtropical region. We collected influenza surveillance data from all medical facilities in Changsha City from 2017 to 2023. The effects of temperature on various influenza indicators, including daily frequency of influenza, influenza-like illness (ILI) rate, influenza A (FluA) rate, and influenza B (FluB) rate, were assessed using the distributed lag nonlinear model. This study revealed temperature exhibited the most significant impact on influenza activity. The low temperature (below 10°C) increased the effect on all influenza indicators, while the high temperature (above 25°C) primarily enhanced the effect on FluA and ILI rates. The impact on populations aged 6-17 years was significantly stronger than on other groups. The research results could provide reference for influenza prediction and early warning.