What is West Nile virus and how is it spread?
West Nile virus (WNV) is a virus found in birds and carried by mosquitoes. When an infected mosquito bites a bird, the bird can become infected and can pass the virus on to other mosquitoes. When an infected mosquito bites a human, the virus can cause mild symptoms to West Nile fever or encephalitis (swelling of the brain). In 2002, West Nile virus caused death and illnesses with lasting effects to some people in Ontario. West Nile virus is not spread by person-to-person contact such as touching, kissing, or caring for someone who is infected.
Are children or infants at greater risk of becoming infected with West Nile virus?
Children, including infants, are not at greater risk than other individuals for becoming infected with West Nile virus. Anyone can become infected with the virus if bitten by an infected mosquito, but children will need an adult's help in taking precautions against mosquito bites. Parents and caregivers should take the following precautions to help protect children from getting mosquito bites.
From April to October, when mosquitoes are most active, take the following precautions:
- If outside from dusk to dawn when mosquitoes are most active, or during the day in shady areas or where there are weeds, tall grass, or bushes, wear protective clothing such as: loose-fitting, lightly coloured long-sleeved shirts and pants as well as socks. Also, consider the use of an insect repellant containing DEET.
Health Canada has released some guidelines for people using repellents containing DEET:
- For children under six months of age insect repellent containing DEET is not recommended
- For children between six months and 12 years of age it should never be used on their face and hands
- For children between six months and two years should only use it when there's a high risk of complications from insect bites and only the least concentrated product (10% DEET or less) should be used sparingly
- For children aged two to 12 years of age should use the least concentrated product and do not apply more than three times daily. Do not apply to the face or hands
- Anyone 12 years of age and older should not use any products with a DEET concentration of greater than 30%
Some Safety Tips for Using Insect Repellents:
- Keep all insect repellent containers out of the reach of children.
- Always supervise the application on children. Avoid applying repellent to children's hands to reduce the chance of getting the repellent in their eyes and mouths.
- If you suspect that you or a child is reacting to an insect repellent, stop using the product immediately, wash the treated skin and seek medical attention. When you go to the doctor, take the product container with you.
- To test if you or a child is sensitive to a product, apply the product to a small area of skin and wait 24 hours to see if a reaction occurs.
- Products that are combination sunscreen and insect repellent are not recommended.
- Products with a low concentration of DEET may be appropriate for situations where exposure to mosquitoes is minimal. Higher concentrations of DEET may be useful in areas with high mosquito populations.
What can I do to help reduce exposure to mosquitoes?
Mosquitoes lay their eggs in standing water. Weeds, tall grass, and bushes provide shelter for mosquitoes.
- Make sure that doors and windows have tight-fitting screens. Repair or replace all screens that have tears or holes.
- Dispose of tin cans, plastic containers, ceramic pots, or similar water-holding containers.
- Make sure roof gutters drain properly. Clean clogged gutters in the spring and fall.
- Eliminate any standing water that collects on the property.
- Remind or help neighbours to eliminate breeding sites on their properties.
If a mosquito bites a child, should he or she be tested for West Nile virus?
No. Most mosquitoes are not infected with the West Nile virus. Even in areas where mosquitoes may be found that carry the virus, very few mosquitoes -- less that 2% -- are infected.
If an infected mosquito bites a child, will he or she get sick?
Most people, including children, who are bitten by mosquitoes carrying West Nile virus, will experience no symptoms or very mild illnesses. If illness were to occur, it would occur within 3 to15 days of being bitten by an infected mosquito.
Should I seek medical attention if I think that a child has become infected with West Nile virus? What are the symptoms?
Even though the chances are slight that a child could become infected with West Nile virus, parents or caregivers should contact a doctor immediately if a child develops symptoms such as high fever with: confusion; muscle weakness; severe headaches; stiff neck; or if his or her eyes become sensitive to light.
The signs and symptoms may include fever, headache and body aches. Some people also develop a mild rash or swollen lymph glands. In some individuals, particularly the elderly, West Nile virus can cause a serious disease that affects brain tissue. At its most serious, it can cause permanent neurological damage and can be fatal. Symptoms of encephalitis (inflammation of the brain) include the rapid onset of severe headache, high fever, stiff neck, confusion, loss of consciousness (coma), or muscle weakness, and may be fatal.
Is a child at risk for becoming infected with West Nile virus while attending school, on field trips or sporting events?
The mosquitoes that most commonly carry West Nile virus are generally more active during evening, nighttime and dawn hours, so children who attend or travel to school during the daytime are at minimal risk for exposure. However, mosquitoes may be active during the day in areas where there are weeds, tall grass or bushes. So if a child will be in or near such areas, it is recommended that she or he wear protective clothing (as described above) and that you consider the use of an insect repellent with DEET.
How is West Nile encephalitis treated?
There is no specific therapy. In more severe cases, hospitalization and intensive supportive therapy may be indicated.
Is there a vaccine for West Nile virus?
No. A vaccine for West Nile virus does not exist.
Who should I contact at Public Health Services for more information?
Last Updated: July 3, 2009