Why is the flu more common in the winter?
New research from Virginia Tech has confirmed that the people are more likely to come down with the flu during the winter, creating a very real "flu season." However, this study has also investigated why such a correlation exists, examining the virus at different climates. Ultimately, the researchers discovered that influenza is most commonly contracted in periods of extremely high humidity (nearly 100 percent – the rainy season in tropical climates) or low humidity (under 50 percent – winter in a temperate climate).
This study was the first in which scientists have successfully observed a relationship between humidity and human mucus production, potentially explaining why the flu season is different depending on the region of the world. The winter in the U.S. and Europe is a time of low humidity; at low humidity, when the virus was added to simulated respiratory fluid, the respiratory fluid evaporated completely, leaving the virus to survive under these dry conditions.