Ottawa resident who tested positive for mosquito-borne virus dies, public health says

The City of Ottawa is reporting the first human case of the mosquito-borne virus eastern equine encephalitis (EEEV).

Ottawa Public Health (OPH) says a resident who died of a viral encephalitis in August tested positive for an eastern equine encephalitis virus infection.

The health unit says like West Nile Virus, EEEV "normally cycles between wild birds and mosquitoes but can occasionally spread to horses and, rarely, to humans through an infected mosquito's bite."

"Humans do not get infected with EEEV from a horse or another human."

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There is no vaccine for humans against EEEV.

In August, the Ontario Ministry of Agriculture, Food and Agribusiness said EEEV had been confirmed in a horse in the Ottawa area.

"A 15-year-old Thoroughbred gelding was ataxic when brought in from the field, was dull and would hang his head down in the corner of the stall. He became recumbent overnight and developed nystagmus in the morning," the ministry said.

The horse was euthanized. Officials say the horse was not vaccinated against EEEV.

Symptoms of EEEV in humans include a fever, headaches, respiratory symptoms and vomiting.

The Public Health Agency of Canada said as of Sept. 12, this is the only confirmed positive human EEEV disease case in the 2024 mosquito season (May to October) in Canada.

"The Public Health Agency of Canada is aware of the recently confirmed human case and subsequent death related to Eastern equine encephalitis virus (EEEV) disease in Ontario, as reported by Ottawa Public Health. Our thoughts are with the family during this difficult time," a spokesperson said.

"Based on available data in Canada, locally-acquired human cases of EEEV are rare. Prior to this case, there had been three locally acquired human cases of EEEV confirmed in Canada by PHAC’s National Microbiology Laboratory since 2016, with the last case being identified in 2022." 

Eight cases of EEEV in horses have been reported across Canada.

Ottawa Public Health is urging residents to protect themselves against mosquito bites to reduce the risk from West Nile Virus and eastern equine encephalitis virus. Tips to protect yourself include:

• Applying a Health Canada-approved mosquito repellent containing DEET or icaridin to exposed skin and clothing (avoid applying DEET to synthetic fabrics)
• Protecting yourself when mosquitoes are active, especially between dusk and dawn and any time you are near shady hedges or bushy or wooded areas
• Wearing light-coloured, tightly woven, loose-fitting clothing, such as long pants, a long-sleeved shirt, shoes and socks, to protect exposed skin
• Making sure all windows and doors in your home have screens that are in good condition

The health unit reported two human cases of West Nile Virus this summer.

In July, a horse tested positive for eastern equine encephalitis virus in Lanark County.