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

Abstract

BackgroundPrevious 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. MethodsData 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 μm (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. ResultsOur 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/m3and 15 g/m3, as well as the same lag period when Min Temp = 5 °C and 20 °C. ConclusionOur 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.