[Persistence of influenza A viruses in relation with environmental factors]

Wild waterfowl represents the natural reservoir of influenza A viruses. Transmission within bird populations occurs through an indirect fecal-oral route implying contaminated water. Within human populations, influenza A viruses can be transmitted through large droplets, aerosols, or direct contact with secretions. Thus, in the human compartment as in the avian one, influenza A viruses have to experiment a free living stage. The knowledge of factors influencing viral persistence during that key step is needed to understand their transmission dynamic. Data gathered here describe the major role played by temperature, pH and salinity on viral persistence in aquatic environment and the importance of UV radiations, humidity and temperature in mid air. We discuss mechanisms underlying these roles and the potential influence of other factors. We point out the need to develop researches to improve our understanding on influenza A virus stability and thus transmission.