High temperature (30 degrees C) blocks aerosol but not contact transmission of influenza virus.

Influenza causes significant morbidity in tropical regions; however, unlike in temperate zones, influenza in the tropics is not strongly associated with a given season. We have recently shown that influenza virus transmission in the guinea pig model is most efficient under cold, dry conditions, which are rare in the tropics. Herein, we report the lack of aerosol transmission at 30 degrees C and at all humidities tested. Conversely, transmission via the contact route was equally efficient at 30 degrees C and 20 degrees C. Our data imply that contact or short-range spread predominates in the tropics and offer an explanation for the lack of a well-defined, recurrent influenza season affecting tropical and subtropical regions of the world.