West Nile virus
West Nile virus is spread by mosquitoes that have fed on the blood of infected birds. Infected mosquitoes pass the virus to people through bites.
Do mosquitoes everywhere carry the virus?
Not every mosquito carries West Nile virus and not every person bitten by a mosquito will get West Nile virus.
In Canada, the virus can be found in mosquitoes in Quebec, Ontario, Manitoba, Saskatchewan and Alberta. Cases have been reported in Atlantic Canada and British Columbia, but to date, these have been travel-related.
If you live in an area where the virus is active, you should protect yourself and your family.
In Canada, infection with West Nile virus almost always happens in August and September unless a person has recently travelled outside of Canada.
The Public Health Agency of Canada keeps track of where the virus is active.
What are the symptoms of infection with West Nile virus?
Usually, people with the virus will have no symptoms. If symptoms do happen, it’s usually between 3 and 14 days after you were bitten by an infected mosquito.
Symptoms are often flu-like and can include fever, aches and fatigue. In very few cases, the virus can cause a serious illness like encephalitis (swelling of the brain), meningitis (brain infection) or paralysis.
Is West Nile virus dangerous to children?
Serious illness from West Nile virus is much more common in adults than children. Most children who get the virus have either no symptoms or only a mild illness. Still, it’s possible for children to get very sick. But this is very rare.
Children with a weak immune system or who already have a serious illness are most at risk of becoming very sick.
What can I do to protect my family?
The best protection against West Nile virus is to avoid mosquito bites. There is no treatment or vaccine to prevent the disease.
If you live in an area where the virus is active, protect your children whenever they are outside.
Help reduce the number of mosquitoes
Mosquitoes breed in standing water (water that isn’t moving), even very small amounts. To reduce the number of breeding spots around your home:
- Drain standing water from items like toys, flower pots, cans, buckets, barrels and pool covers often.
- Remove things where water can collect, like old tires.
- Clean or change the water in swimming pools, decorative pools, children’s wading pools and bird baths often.
- Clean out clogged gutters.
- Cover rain barrels with screens.
Reduce the chance of being bitten
- Mosquitoes are most active at dawn and dusk. Wear protective clothing or using insect repellant if you go outside at these times.
- Windows and doors should have a screen that fits tightly and has no holes.
- Use mosquito nets or screens for baby strollers.
- Wear protective clothing when possible: light-coloured clothing with long sleeves and cuffs, long pants tucked into socks or shoes, and hats are recommended.
Use insect repellents
Insect repellents don’t kill mosquitoes, but they help keep mosquitoes away. Read Caring for Kids information on using insect repellents in children.
More information from the CPS
Reviewed by the following CPS committees
- Infectious Diseases and Immunization Committee
Last updated: December 2019