This may be a little off topic but 160 years ago there was a similar debate going on concerning the cause of cholera.
John Snow plenty of good data yet most refused to believe him.
Here are a few of links:
http://www.umapper.com/maps/view/id/43438/
http://en.wikipedia.org/wiki/John_Snow_%28physician%29
http://en.wikipedia.org/wiki/1854_Br...olera_outbreak