Researchers say, in temperate regions, such as North America and Europe, flu season peaks during the winter when humidity is low. That's when, they say, the virus's viability in mucus increased when the relative humidity is below 50 percent.
Researchers found that when the humidity is low indoors in the winter respiratory droplets evaporate completely. And under these dry conditions the virus is better able to survive.
The research is published in the journal PLOS ONE .