West Nile Virus

February 1, 2017 at 11:56pm

For most Canadians, the risk of illness from West Nile virus is low, and the risk of serious health effects is even lower. It is still important to know the symptoms of illness related to infection and how to minimize your risk, especially if virus activity is reported in an area near you. Also provided below are answers to some frequently asked questions and additional West Nile links.

The evidence to date shows that most people with West Nile virus contracted it from the bite of an infected mosquito. A mosquito becomes infected when it feeds on the blood of a bird that carries the virus. About two weeks later, the infected mosquito becomes capable of spreading the virus.

In 2002, scientists discovered other ways that West Nile virus could be spread, i.e. through blood transfusions and organ or tissue transplants. The risk of getting WN virus through these procedures is considered to be quite low. There is evidence the virus can also be spread through breast milk, and from a pregnant mother to her unborn baby. In addition, laboratory workers who handle specimens with WN virus can become infected through needle punctures or small cuts.


Most people who become infected have no symptoms, and do not get sick. When infection does cause illness, symptoms generally appear within two to 15 days. In mild cases, people may have flu-like symptoms including fever, headache and body aches. Some may also develop a mild rash or swollen lymph glands.

Some individuals, including older people, have weaker immune systems. This puts them at greater risk for serious health effects including meningitis (inflammation of the lining of the brain or spinal cord) and encephalitis (inflammation of the brain).

In these cases, symptoms could include: Rapid onset of severe headache; High fever; Stiff neck; Drowsiness; Confusion; Loss of consciousness; Muscle weakness; and, Paralysis. Severe cases of illness due to West Nile virus can be fatal.

Anyone who experiences the sudden onset of these symptoms should seek medical attention.

Minimize the Risk

Your chance of being bitten by a mosquito capable of spreading the West Nile virus is small. If, however, there are reports of infected mosquitoes, infected horses or dead birds in your area, you should take immediate action to minimize your risk of mosquito bites by:

  • Limiting the time you spend outdoors at dawn and dusk, when mosquitoes are most active.
  • Wearing light-coloured long-sleeved shirts, long pants and a hat when outdoors.
  • Using insect repellents (read and follow the manufacturers` directions for safe use).
  • Making sure that door and window screens fit tightly and have no holes.
  • Reduce mosquito populations around your home and property by removing standing pools of water, which they use to breed. Empty and clean bird baths twice a week.
  • Clean eaves troughs regularly to prevent clogs that can trap water.

Q. Can you get West Nile virus through casual contact?

  • A. There is no evidence to suggest you could get the WN virus by touching or kissing an infected person, or from being around a health care worker who has treated an infected person. Additionally, there is no evidence the virus can pass from infected animals, such as horses or pets, to people.It is, however, still important to follow standard health and safety practices if you are going to handle dead birds or animals. The same is true if you work with animals at risk for WN virus infection, such as horses, or flocks of domestic birds. For example, you should cover open wounds and wear protective gloves.

Q. Who is at risk for serious health effects from WN virus?

  • A. While persons of any age and health status can be at risk for serious health effects associated with West Nile infection, the overall risk of serious health effects increase with age. People with weaker immune systems are considered to be at greater risk for serious health effects. This higher risk groups includes: People with chronic diseases, such as cancer, diabetes, alcoholism or heart disease. People that require medical treatment that may weaken the immune system, i.e. chemotherapy.

Q. What are the long-term effects of WN virus?

  • A. Because WN virus is an emerging disease, the long-term effects are not fully understood. Studies to date show that some people with serious symptoms and health effects recover completely, while others experience prolonged health problems.These problems can include: Physical effects, such as long-term muscle weakness and paralysis, fatigue and headache; Cognitive effects, such as confusion, depression, problems with concentration and memory loss; and, Function effects, such as difficulty with preparing meals, going out, shopping etc. Scientists do not know why some people recover while others continue to have varying degrees of health problems.

Q. What can I do to protect myself and my family?

  • A. To protect yourself and your family, you should avoid being bitten by mosquitoes. You can take action by minimizing your exposure to mosquitoes by: Using insect repellents that contain DEET or other approved ingredients. Trying to avoid spending time outdoors at dawn and at dusk when mosquitoes are most active. Wearing protective clothing such as long-sleeved shirts, long pants and a hat. Light coloured clothing is best because mosquitoes tend to be more attracted to dark colours.You can also eliminate breeding sites around your home and cottage by getting rid of standing water around your property by: Draining standing water from items like pool covers, saucers under flower pots, recycle bins, garbage cans etc. Removing old unused items from around your property including old tires. Changing the water in wading pools, bird baths, pet bowls and livestock watering tanks twice a week. Covering rain barrels with screens. Cleaning out eaves troughs regularly to prevent clogs that can trap water.