For the first time this summer season, mosquitoes in Toronto have tested positive for West Nile Virus

Toronto Public Health announced Wednesday it had received a lab report indicating mosquitoes in Toronto have tested positive for the virus.

The city agency keeps 43 mosquito traps throughout the city and submits mosquitoes for laboratory testing every week. This is the first positive test of 2013.

Elaine Pacheco, Healthy Environments Manager for Toronto Public Health, said the positive test is a reminder to the public to protect themselves from mosquitoes and remove standing water from their property, where mosquitoes can breed.

West Nile Virus is transmitted by mosquitoes that become infected by feeding on the blood of infected birds.

Although the majority of those infected never show symptoms, around 1 per cent will become ill enough to be hospitalized. The chances of severe illness are greater in older people, even those who are healthy.

West Nile Virus was first discovered in Toronto in 2001. In 2012, Toronto Public Health reported 94 known human infections.

Symptoms can include fever, headaches, nausea, vomiting and body aches. These can also be accompanied by a skin rash and swollen glands.More serious symptoms include neck stiffness, extreme confusion, disorientation, muscle weakness, vision loss and numbness.

Symptoms of infection usually develop between two and 15 days after being bitten by an infected mosquito.

Although the risk of becoming infected with West Nile is low, Toronto Public Health reminds residents to take precautions throughout the summer to protect themselves:

  • wear light-coloured, long-sleeved shirts, pants, socks and a hat when outdoors, especially at dusk and dawn, when mosquitoes are most active
  • use insect repellent approved by Health Canada and follow product instructions
  • regularly remove standing water from property where mosquitoes can breed
  • maintain screens on windows and doors to keep mosquitoes out of your home

As part of the City of Toronto's West Nile Virus mosquito-reduction program, catch basins and other areas of standing water are treated with larvicide to reduce mosquito breeding.