This is a pretty interesting article about the Flu virus and humidity:
the researchers found the virus survived best at humidity below 50%, similar to the conditions found indoors in “a really heated building,” says Dr. Marr. “The virus is happy if the mucus droplet completely evaporates and leaves it floating around” in the air.
“It’s also fine in humidities above 98%, which you find in the rainy season in the tropics,” she says, where the conditions outside resemble the environment the virus finds in the body. “But in between, in a humidity of 50% to 98%, the virus doesn’t survive very well.”
If offices, schools and other places where people congregated were to install humidifiers and keep a closer eye on building humidity, would flu’s be less problematic? In theory it could actually save a business money to pay attention to the humidity in the building and keep employees from getting sick.