Health officials in Ontario’s Peel Region are reminding people to protect themselves against insect bites after mosquitoes carrying West Nile virus were found in Brampton.
The virus can be transmitted to humans through bites from infected mosquitoes, and 70 to 80 per cent of people who get it show no symptoms.
Symptoms can include fever, headache, swollen lymph glands and mild rashes, and can show up for up to 15 days after infection.
In more serious cases, some people can develop more severe or long-term symptoms like muscle weakness, loss of consciousness and paralysis. In incredibly rare cases, the disease can be fatal. Immunocompromised individuals, people with chronic conditions like diabetes or heart disease and elderly people are more at risk than others.
Health Canada tracks West Nile virus in Canada with the help of various provincial partners and agencies and, so far, there have been no reported infections in humans this year.
Curtis Russell, a senior program specialist at Public Health Ontario (PHO), told HuffPost Canada that this year has been relatively quiet compared to previous ones in the province. He noted that this time last year, PHO had identified 16 mosquito pools that tested positive for the virus — this year, they’ve only had two.
“A big thing with mosquitoes and West Nile virus is temperature drives a lot of this, you know the higher the temperatures are the faster the mosquitoes develop but also the higher the temperature… the faster the virus will replicate and spread throughout the mosquito so that it can transmit it,” Russell said. “In general, we had a very cool wet spring and even the start of our summer was relatively cool so that would slow a lot of things down.”
Still, Russell cautioned that the worst of the summer could still be ahead as temperatures continue to warm up and the disease has time to build up.
“We expect to see more positive mosquito pools… there’s a lot of factors that really come into play but right now we have low numbers compared to some of the previous years, but we do expect to see some increase in activity now.
Taking precautions
Russell said that despite the fact that most people show no symptoms, people should still take preventative measures like wearing long sleeves, light-coloured clothing, and using insect repellants that contain the chemicals DEET or Icaridin. If possible, they should also avoid going out during dusk and dawn, when mosquitoes are most active. He also said people should try to make the areas around their homes less hospitable to the types of mosquitoes that carry the virus.
“The main mosquitoes that primarily transmit this are mainly more urban mosquitoes. They really like standing water with organic matter so wash out your birdbaths, any other stuff with organic debris and [water] in it. Try to wash those out on a regular basis so you don’t give them habitat to develop.
Once the first frost of the fall hits an area, its residents can relax about the risk of West Nile, Russell added.
“Once you get that first frost you’ve kind of killed off most of the mosquitoes… so you probably don’t have to worry.”
The first case of West Nile in a person in Canada was in Ontario in 2002. The government has tracked cases since then, with 2007 being the year with the highest rate of infections in humans — at least 2,215 people in Canada had the virus. In 2018, 427 were reported to have the virus.
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