Mosquitoes carrying West Nile virus found in five locations in Toronto

Toronto Public Health is aware of five pools of mosquitoes in the Toronto area that have tested positive for West Nile virus. The mosquitoes, found in locations in Etobicoke, North York and west Toronto, are the first to test positive for West Nile virus in Toronto this year. Human infection with West Nile virus most often occurs from July to the end of September. Infections are usually asymptomatic, with only about 20% of infected people developing symptoms. The number of reported human cases annually likely underestimates the true burden of West Nile virus disease. People older than 50 years of age are at increased risk of West Nile virus neuroinvasive disease, which carries a risk of permanent neurologic damage or death. West Nile virus neuroinvasive disease should be suspected in patients with fever and acute onset of encephalitis, viral meningitis, acute flaccid paralysis, tremor, myoclonus or Parkinsonian-like condition. West Nile virus should also be considered in older adults with acute confusion or altered mental status. Read: Physician and pharmacist team up to offer hair loss solutions Although no specific treatment is available for West Nile virus neuroinvasive disease, diagnostic suspicion can help prevent mistakenly attributing the symptoms to other causes of altered mental status (e.g., dementia, stroke). Toronto Public Health recommends that healthcare providers consider ordering West Nile virus serology during the summer months for patients who have at least two of the following symptoms with no apparent alternate cause: fever, myalgia and/or arthralgia, headache, fatigue, lymphadenopathy, maculopapular rash. Public Health Ontario guidelines for serology testing are available here. Toronto Public Health is reminding healthcare providers to report suspected cases of West Nile virus to the Medical Officer of Health by phone (416-392-7411) or fax (416-392-0047) within 24 hours. Healthcare providers can play a key role in educating patients about ways to reduce the risk of West Nile virus infection. The most important way is to avoid mosquito bites. Patients should be advised to: Take extra care during peak mosquito biting time (dusk and dawn) by using mosquito repellent and wearing protective clothing (light-coloured, long-sleeved shirts and pants) when outdoors. Apply insect repellent containing N,N-diethyl-meta-toluamide (DEET) or icaridin (follow the manufacturer’s instructions). The City of Toronto’s West Nile virus webpage includes information on which concentrations of DEET are appropriate for various age groups. Remove standing water from your property, where mosquitoes can breed. Ensure your home has tight-fitting screens on windows and doors. Reference 1. Poser J. Update: West Nile virus 2022. Toronto Public Health's Physician e-Newsletter, August 9, 2022. (accessed August 11, 2022)

Mosquitoes carrying West Nile virus found in five locations in Toronto

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