Primarily transmitted to humans through the bite of an infected mosquito, West Nile Virus is an arthropod-borne virus that typically shows few or no symptoms in humans, but in rare cases, can be fatal.
Anyone that spends time outdoors is at risk of West Nile, however the risk varies from year to year depending on the amount of rain, how hot it gets, and the current population of mosquitoes. Mosquito populations reach their peak in the summer months, so right now is the time to be protecting yourself against mosquitoes.
How does Canada monitor West Nile Virus?
Canada saw its first human case of West Nile Virus (WNV) in Ontario in 2002. Since then, the data has gone through a number peaks and troughs, with the most notable outbreaks occuring in 2003 (1481 cases), 2007 (2215 cases), and 2012 (428 cases).
From April to October, provincial and territorial health ministries and blood supply agencies across Canada conduct ongoing human case surveillance of WNV. These numbers are then reported to the Canadian government. Surveillance efforts work to detect a portion of WNV cases, but with the lack of symptoms evident in humans, the real number of infections is likely to be much greater.
What is the current situation?
In 2015, 80 cases of WNV were reported in Canada. So far, there isn't any data for human infections in Canada yet, however in mid-July, mosquitoes themselves tested positive for West Nile in Mississauga, Ontario while just this week, a trap taken from Mitchell (a community in Perth County, Ontario) tested positive for WNV, the first since 2013.
With Summer in Ontario being much hotter this year than usual, it makes sense that residents are noticing increased mosquito activity. And with positive tests turning up in Mississauga and Mitchell, it's especially important for Ontario residents to protect themselves from mosquito bites.
UPDATE (August 2, 2016): Manitoba has now detected West Nile in mosquitoes found in Altona, West St. Paul, and Winkler. Although Culex tarsalis mosquitoes (the ones that spread West Nile) are currently present throughout southern Manitoba, there are still no human cases reported.
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