Effect of short-term ambient temperature exposure on influenza A and B incidence: a time-series analysis of daily surveillance data in Kawasaki City, Japan.

Objectives: Although there is epidemiological evidence that ambient temperature affects influenza transmission, the relationship between temperature and specific influenza virus types remains inadequately studied. This study aimed to investigate the association between ambient temperature exposure and the incidence counts of influenza A and B viruses in Kawasaki City, Japan. Methods: Daily data on influenza A and B cases and meteorological variables were collected from Kawasaki City, Japan, spanning from March 2014 to December 2019. A time-series quasi-Poisson regression model, in conjunction with a distributed lag non-linear model, was utilized to explore the exposure-response relationship between short-term influenza risk and daily mean temperature. Results: The study encompassed 181,895 patients with influenza. Our findings indicated that cold temperatures significantly heightened the risk of influenza A and B virus infections. The overall cumulative relative risk of influenza A was 5.08 (95% confidence interval 3.64-7.08) at cold temperatures (5 Conclusions: This study suggests that the short-term effects of temperature on influenza transmission are type-specific. It offers crucial insights for future research on the complex associations between ambient temperature and respiratory infectious diseases.