Want To Avoid The Flu? Moisture Is The Key

WASHINGTON (AP) - Studies of seasonal influenza have long found indications that
flu spreads better in dry air.
Research in the Proceedings of the National Academy of Science
indicates that the key is the absolute humidity which measures the
amount of water present in the air, regardless of temperature - not
the more commonly reported relative humidity.
Relative humidity varies depending on air temperature; absolute
humidity doesn't.
The correlation with flu and low humidity is important because
in cold winter weather, when flu is most common, even a high
relative humidity reading may indicate little actual moisture in
the air. The less moisture there is, the happier the flu virus
seems to be.
Still, overdoing the moisture can cause other problems, like
mold.

(Copyright 2009 by The Associated Press. All Rights Reserved.)

You can find more on the article in the Proceedings of the National Academy of Sciences here.