Canada watching mosquito-borne illness after parks shut down in U.S.

Health officials in Canada are closely monitoring the public health situation in Massachusetts, following a report of one person having contracted Eastern Equine Encephalitis (EEEV) from a mosquito bite. A man in his 80s caught the disease, becoming the first known human case of EEEV in that state since 2020.

Ten Massachusetts communities have shut down parks and fields after dark and are urging some residents to minimize outdoor activities.

“EEEV is endemic to Canada; however, the diagnosis of EEEV in humans is a rare occurrence," wrote the Public Health Agency of Canada in a statement to CTV News. 

"There have been only four confirmed locally acquired human cases of EEEV in Canada reported since 2016, the most recent of which was in 2022."

Sporadic cases of EEEV in horses are observed each year and are immediately notifiable to the Canadian Food Inspection Agency. As of August 17, 2024, there have been no human cases and six confirmed cases of EEEV in horses (five in Ontario and one in Quebec) reported for the 2024 mosquito season. PHAC is taking a "One Health" approach, recognizing the interconnections between people, animals, plants and their shared environment, and is working with human and animal health partners to monitor the situation closely. 

"Currently, while the overall risk of EEEV in humans is low in Canada, some local public health units in Canada have recommended taking precautions in areas where recent EEEV activity in horses has been reported.”

Infectious diseases specialist Dr. Lisa Barrett said mosquitoes carrying the virus usually are the type of mosquitoes that come out at night. To avoid contact, people living in higher-risk areas should do fewer outdoor activities in the evening.

“There are some things you can do to reduce risk,” said Dr. Barrett, like staying away from water, covering your skin with long sleeves and pants and wearing lots of insect repellent.”

Dr. Barrett is not surprised Massachusetts officials are taking the risk seriously.

“The virus is not contracted human-to-human and occasionally, if an infected mosquito bites a human, then of those people bitten it can cause an infection and it has a high fatality rate,” said Dr. Barrett, who added the death rate is between 30 and 50 per cent and symptoms usually show up within roughly 10 days. “They will have a fever, headache, changes in how they were thinking and being very confused, plus sometimes diarrhea and muscle aches.”

Dr. Barrett added that, in rare cases, children and older people who contract the virus could experience brain inflammation, which could lead to permanent disability.