High rates of West Nile virus found in Toronto mosquitoes
Published Wednesday, August 1, 2012 7:11PM EDT
Toronto is recording a higher-than-usual frequency of mosquitoes carrying West Nile virus, according to Toronto Public Health.
Of the 43 bug traps set up around the city, 24 of them have captured mosquitoes that tested positive for West Nile.
This is the highest rate in Toronto in 10 years of monitoring for the disease.
The higher number is likely due to the warm weather, said Toronto associate medical officer of health Dr. Howard Shapiro.
“The heat drives the multiplication of the virus in the mosquitoes, relies on the ambient temperature, and so although the number of mosquitoes is the same, the amount of virus in them is a lot higher,” Shapiro told reporters at a news conference Wednesday.
Because the disease can be transmitted to humans, public health officials are telling doctors to be on alert.
“There may be someone who could be ill right now, but the time it takes for them to see a doctor, have the test, and the test reported back to us does take a while,” Shapiro said.
Four out of five people who are bitten by a mosquito with West Nile will have no symptoms, but the virus can cause fever, headache and fatigue.
One in 100 people with the disease can have brain swelling, which requires hospitalization and can be fatal.
There are no human cases reported in Toronto and, in an effort to keep it that way, the city has increased its larva eradication program in which city staff put small amounts of pesticide in 120 catch basins in the city.
The pesticides keep the mosquitoes in the pupae stage, meaning they cannot eat and will eventually die.
While there are more mosquitoes in rural areas, urban mosquitoes are actually more likely to be infected with West Nile.
This is because the main carriers of the virus prefer city environments, where the water is more polluted and there are fewer natural predators.
Public health is also warning people to check their home screens to ensure they are sealed, wear bug repellant and wear long sleeves and pants when outside.
With files from CTV Toronto’s Natalie Johnson