Experts say global warming could spread disease

CTV.ca News Staff With a report by CTV’s David Akin

Canadian winters can be an effective defence against the spread of tropical diseases and pests, but experts say that could change with global warming.

“Either the geographical distribution can become more extensive for diseases … or the duration of the season of risk can increase,” Dr. Neil Rau, an infectious diseases expert, told CTV News.

“Or even more unusually, someone can import a new disease, the way West Nile came to North America.”

Mosquitoes carry West Nile to humans after consuming the blood of infected birds, and warmer winters mean more mosquitoes carrying the disease.

“That dramatically increases the chance that a human will be bitten by one of those infected mosquitoes towards the end of the summer,” said Dr. Brian Ward, a tropical diseases expert at the University of McGill.

Another concern is ticks that carry lyme disease. They’re usually found only in the warmest parts of Canada, like southern B.C. and the shoreline of Ontario’s Lake Erie.

“But much of Canada is appropriate tick habitat, and so if there were to be global warming it seems very reasonable that we might see the ticks extend their range into a much larger part of Canada,” said Ward.

Lyme disease is already the fastest-growing infectious disease in the U.S., and appeared in Nova Scotia for the first time just two years ago. It can be very painful and difficult to treat.

“It is going to be very important that not only the public is made aware of this, but that the medical profession knows what to look for,” said Dr. Paul Sockett of Canada’s Public Health Agency.

CTV’s David Akin reported that there are several other ways that global warming could contribute to the spread of disease.

“When there are extreme weather events like flooding, researchers are finding new strains of E. coli,” he said. “And with soils warming up on the west coast, researchers have found some funguses that are carrying diseases.”

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