Effect modification of environmental factors on influenza-associated mortality: a time-series study in two Chinese cities

Abstract

Abstract Background Environmental factors have been associated with transmission and survival of influenza viruses but no studies have ever explored the role of environmental factors on severity of influenza infection. Methods We applied a Poisson regression model to the mortality data of two Chinese metropolitan cities located within the subtropical zone, to calculate the influenza associated excess mortality risks during the periods with different levels of temperature and humidity. Results The results showed that high absolute humidity (measured by vapor pressure) was significantly (p Conclusions These findings highlight the need for people with chronic cardiovascular and respiratory diseases to take extra caution against influenza during hot and humid days in the subtropics and tropics.