Dr. David N. Fisman, a professor at the Dalla Lana School of Public Health at the University of Toronto: It is difficult to be certain that climate change is a factor but it seems plausible, he said. The bacteria is more infectious in warm temperatures and some studies, including one he and others did in 2005, have shown that wet, humid weather predicts an upsurge in the risk of contracting the disease over the following week or two. That finding was not replicated in Toronto, he said, but there the disease peaks later in October in that area.
