How is West Nile virus spread?
West Nile virus is spread by infected mosquitoes. Not every mosquito carries West Nile virus and not every person bitten by a mosquito will be infected with West Nile virus. But if you live in an area where the virus is active, you should protect yourself and your family.
In Canada, the virus peaks in late August to early September.
Do mosquitoes everywhere carry the virus?
In Canada, the virus can be found in mosquitoes in Quebec, Ontario, Manitoba, Saskatchewan and Alberta. There have been cases reported in Atlantic Canada and British Columbia but they have been travel related.
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 have been 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 (a swelling of the brain), meningitis (a brain infection) or paralysis.
Is West Nile virus dangerous to children?
Serious illness from West Nile virus is more common in adults than children. Most children who get the virus will have only a mild illness. Still, it’s possible for children to get very sick. But this is very rare.
Children with weak immune systems or who already have a serious illness are most at risk of becoming very sick.
What if I am pregnant or breastfeeding?
There is at least one known case of a pregnant woman passing on the virus to her unborn baby. The baby was born with serious medical problems. However, it isn’t clear if the virus was the only factor involved. No more cases have been found to date despite many pregnant women having evidence of the infection.
In another case, a mother passed on the virus through her breast milk, but her baby didn’t show any symptoms. It isn’t necessary for infected women to stop breastfeeding.|
Although pregnant women are no more at risk than other people, you should take care to prevent mosquito bites.
What can I do to protect my children?
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 when they are outside, whether at home, school, day care or camp. Here’s what you can do:
Help reduce the number of mosquitos
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 and 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 your chance of being bitten
- Mosquitoes are most active at dawn and dusk. Spend less time outside during these times.
- Windows and doors should have screens that fit tightly and have 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 make us unattractive to them. The only products proven to work outdoors for a long period of time are those that contain DEET.
Not all products have the same concentration (amount) of DEET. The amount of DEET in a product is shown as a percentage, such as 10% DEET.
Insect repellents used on children should have a small concentration of DEET, depending on the age of the child. DEET should not be used on children younger than 6 months.
- For children between 6 months to 2 years, use products with 10% DEET or less, only once a day.
- For children between 2 and 12 years, use products with no more than 10% DEET, up to 3 times a day.
- For children over 12 years, use products with 30% DEET or less. Re-apply when it’s no longer working. The number of hours your child will be protected depends on how much DEET is in the product.
More information from the CPS:
Other resources:
- Public Health Agency of Canada
- West Nile virus: Pregnancy and breastfeeding
- West Nile virus surveillance
Reviewed by:
CPS Infectious Diseases and Immunization Committee
Last updated: June 2008
