henry copeland:

Exercising to avoid the flu? It’s all about the sweet spot - The Globe and Mail

a 2011 study of 1,002 adults by Dr. David Nieman at Appalachian State University found that those who exercised five or more days a week were 43 per cent less likely to develop upper respiratory tract infections during the fall and winter than those who exercised once a week or less.
- www.theglobeandmail.com