Interactive effect of air pollutant and meteorological factors on seasonal influenza transmission, Shanghai, China

Background: Previous studies have provided evidence of seasonal influenza transmission linked to various meteorological and environmental factors. However, the joint effect from both air pollutant exposure and meteorological factors that modify the seasonal influenza incidence is not well discussed.Methods: Data on weekly laboratory-confirmed influenza positive case numbers were obtained from Pudong New Area, Shanghai, China between January 1, 2011 and December 31, 2019. Weekly average weather data (absolute humidity (AH), minimum temperature (Min Temp) and particulate matter <2.5 mu m (PM2.5) concentration levels) at the same period were collected from Copernicus Atmosphere Monitoring Services (CAMS).A General additive model (GAM) and distributed lag nonlinear model (DLNM) with Quasi-Poisson likelihood were used to evaluate the independent and interaction effect of weather factors and PM2.5 on seasonal influenza transmission along with lag effects.Results: Our research showed that both AH and Min Temp had U-shape interactive relationships with PM2.5 at high PM2.5 concentration level. Interaction between PM2.5 and AH had positive relative risk (RR) effect at lag of 5 weeks when AH = 5 g/m(3 )and 15 g/m(3), as well as the same lag period when Min Temp = 5degree celsius and 20degree celsius.Conclusion: Our study found that an interactive effect between air pollutant and weather factors exists and significantly affects influenza transmission. For future studies, lag interactive effects among air pollutant and temperature or humidity should be considered in the evaluation of the environment-influenza association, as such interactions might change the disease response to short-term effects.

Automated summary

This study found that there is an interactive effect between air pollutants and weather factors, which significantly affects influenza transmission. Future research should consider the interactive effects between pollutants and temperature or humidity to evaluate the environment-influenza association.