Global warming may facilitate spread of mosquito-borne diseases in Canada: expert

Rates of mosquito-borne illnesses are on the rise globally, a trend experts say will continue as the climate warms, presenting new health concerns for Canadians.

Epidemiologists warn that warmer temperatures may allow new species of disease-carrying mosquitos to migrate north into Canada, bringing with them the risk of diseases such as Zika virus and dengue fever.

“It’s easy to see the effects of climate change with ticks,” Dr. David Fisman, epidemiologist at the University of Toronto’s Dalla Lana School of Public Health, told CTV’s Your Morning.

“Twenty-five years ago, when I graduated from med school, we didn’t really have Lyme disease. Now we do… that’s because those creatures have expanded their range north as the weather has gotten warmer.”

Research shows that the same migration pattern is now happening in mosquitos, particularly with the Aedes Aegypti species which is known for spreading diseases including Zika virus, yellow fever, and dengue fever.

Although the species is typically found in tropical environments, warmer temperatures have allowed it to travel further north.

The species was first reported in Ontario in 2017. However, according to Public Health Canada, there is no evidence that Aedes mosquitos found in Canada carry any exotic mosquito-borne illnesses.

But, according to Fisman, that could change if our climate continues to warm.

“For infectious diseases to emerge we think about something called a reproduction number—for it to explode you need each old case to create more than one new case,” he explained.

“In mosquito-borne diseases that’s really dependent on their biting rate, which is a function of temperature. So, the warmer is gets, the more infectious the diseases get.”

Experts note that the effect of climate change on mosquito-borne illnesses is hard to predict.

Research published by Public Health Canada in April notes that the exact impact of climate change on exotic mosquito-borne disease emergence in Canada is “difficult to quantify,” but notes there is a higher risk for those diseases to become native if the right conditions are present.

“Canadians need to be aware of the exotic MBDs that they are at risk for while travelling abroad as disease risk will only increase with climate change,” read the report.

“Further, Canadians returning home serve as a potential route of introduction for exotic mosquito-borne diseases, making the need for awareness even more urgent.”

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