How is West Nile Virus spread?
Mosquitoes become infected with West Nile virus when they feed on the blood of infected birds. The virus is carried in the mosquito’s salivary glands. An infected mosquito can then transmit WNV to humans and animals, when it eats blood. The virus is not known to spread from personal contact such as touching, kissing, or caring for someone who is infected. Other modes of transmission are under investigation.
Should I be concerned?
In 2003, West Nile virus caused death and illnesses with lasting effects to some people in Ontario. If you are bitten by an infected mosquito, you may not get sick but for some, obvious symptoms may occur such as fever, muscle aches and sometimes skin rashes. A smaller number of infected people can get very sick and experience serious lasting illness, even death.
Do all mosquitoes that bite humans transmit the West Nile virus?
No, there are a number of species of mosquitoes in Ontario. Not all of these bite humans and fewer still can carry the virus. Only adult female mosquitoes bite humans. Male mosquitoes feed on plant nectar. Most female mosquitoes feed on humans, birds and other animals to get enough blood to develop their eggs.
Mosquitoes live in urban and suburban areas laying eggs in very shallow, standing and even polluted water.
What attracts mosquitoes to humans?
Cologne, perfumes and scented body lotions can attract mosquitoes. Dark coloured clothing is also more attractive to mosquitoes. Some people produce odours that are attractive to mosquitoes.
Are there certain times of day when mosquitoes bite most?
Mosquitoes are active during evenings until early morning looking for a blood meal, so people outdoors during that time are more likely to be bitten. However, mosquitoes that carry the virus, are active during the day - don't let your guard down any time during the day.
Where do mosquitoes live?
Mosquitoes lay their eggs in deep or shallow standing water around the home. Weeds, tall grass, and bushes provide an outdoor home for them.
Are older adults more at risk from illness associated with West Nile virus?
Older people are at no greater risk of being bitten by a mosquito infected with the West Nile virus than any other person. The elderly and people with weakened immune systems have the highest risk of developing severe illness because as we age, our bodies have a harder time fighting off disease. However, people of all ages can be infected with West Nile virus and some will have severe illness with lasting effects.
What are the symptoms of West Nile virus?
When an infected mosquito bites a human, the virus can cause a range of symptoms from mild to severe. The illness can range from West Nile fever to more severe encephallitis or meningitis (swelling of the brain) and even death.
How is West Nile virus treated? Is there a vaccine?
There is no specific treatment or vaccine against West Nile virus. The symptoms and complications can be treated. Most people recover from an infection.
What can I do to reduce my risk of becoming infected with West Nile virus?
It is recommended that you wear long-sleeved shirts, long pants, socks and shoes when outdoors in areas where mosquitoes are present. If you choose to use an insect repellent, use a repellent that contains DEET (N, N-diethyl-m-toluamide). Follow the manufacturer's directions carefully. DEET is not recommended for children under the age of two.
What can I do around my home to protect myself from exposure to mosquitoes?
Remove or change all standing water around your home (i.e. turn over or throw out containers that hold water, change water in bird baths twice a week) to reduce potential mosquito breeding areas.
Do you have information translated into other languages?
Yes. You can find our factsheet on Important Facts that You Should Know about West Nile Virus in a number of languages.