Is climate change to blame for latest West Nile virus outbreak?

In an average year, there are about 300 cases of West Nile virus reported to the U.S. Centers for Disease Control and Prevention by August. This year there have been 1,118 cases reported, with 42 deaths.

"We're in the midst of one of the largest West Nile outbreaks ever seen in the United States," said Dr. Lyle Petersen, director of the Division of Vector-borne Infectious Diseases at the CDC in Atlanta, Georgia. "The peak of West Nile virus epidemics usually occurs in mid-August, but it takes a couple of weeks for people to get sick, go to the doctor and get reported. Thus we expect many more cases to occur."

In Canada, reports are on the rise, with 49 confirmed cases so far in Ontario, 5 in Manitoba, 2 in Quebec, 1 in Saskatchewan and 1 in Alberta.

"I suspect this year will be another outbreak year, maybe even as big as 2007 or 2003 given the early activity in Ontario," said Dr. Bonnie Henry, Director of Communicable Disease Prevention and Control Services at the B.C. Centre for Disease Control.

Amid concerns about the use of pesticide to combat mosquitoes, there are questions about why the number of cases this year is on the rise. A likely culprit is climate change.

Studies have shown that mosquitoes pick up the virus more easily at higher temperatures and warmer weather makes transmission of the disease easier as well.

"Hot weather seems to promote West Nile virus outbreaks." Peterson said, according to USA Today.

With warmer weather expected due to climate change, including longer summers, and the strong connection between temperature and West Nile, outbreaks of the virus can only get worse in years to come.