"In the winter, we spend more time inside in close contact with other people, and so viral illnesses spread more easily. Bottom line, that is the main reason for the large scale winter phenomenon..." -Tom Wilson, MD PhD

This being-indoors-causes-flu-in-the-winter theory seems to be the most popular explanation of seasonal (winter) flu outbreaks and, until about an hour ago, I accepted it as fact.

Then I saw today's Flu Map from the CDC.



While looking at this map, keep in mind that it's 34F in Bangor right now and 70F in Phoenix.

According to the indoors-causes-flu theory, there should be a whole lot of flu activity in Bangor and very little in Phoenix. That’s because, as the theory goes, cold weather (34F) has the people of Bangor indoors passing around the flu virus while the Phoenicians are outside playing golf in the nice weather (70F).

This isn’t what the Flu Map shows.

Instead, this weeks flu activity is the opposite of the flu activity predicted by the indoors-causes-flu theory: Widespread in Arizona and only Sporatic in Maine.

This, of course, tells me absolutely nothing about how the flu is really spread- but I do know that it has very little to do with being indoors.