What you need to know about Ontario’s summer health risks – CTV
July 01, 2025
As Ontario enters peak summer season, infectious disease experts are warning that some viruses — from respiratory bugs to mosquito-borne illnesses — thrive in the heat.
While many people may consider winter to be the season when they are most at risk of catching a virus and becoming ill, experts who spoke to CTV News Toronto said that there are many infections that actually peak in the summer.
Dr. David Fisman, a professor of epidemiology at the University of Toronto’s Dalla Lana School of Public Health, said that respiratory infections like rhinovirus, enterovirus and para-influenza are all more common in the summer months and are capable of causing mild illness.
He also said that other more serious health threats, like measles, can “come back” when people make a decision to skip vaccination.
Ontario reported fewer new measles cases this past week; 33 compared to 96 the week before, officials say the outbreak now stands at 2,212 cases since October.
