West Nile Virus (WNV)


What is West Nile virus?

The West Nile Virus (WNV) is a virus which can be transferred to humans when an infected mosquito feeds.  Infection may result in no symptoms, in mild illness such as ‘West Nile fever’, or in serious neurological illness such as encephalitis (swelling of the brain).

The species of mosquitoes that are able to transmit WNV has a very low population in the Thunder Bay district.  The Health Unit monitors mosquito species population in the district during the summer months.


What are the symptoms of West Nile virus?

If you have any of the following symptoms, get medical help. Early symptoms of West Nile virus illness kook like many other illnesses, so it is important to get medical attention to find out the cause.

About 1 out of 5 infected individuals will show symptoms. Most people who become infected will experience no symptoms or have very mild illness.

  • Fever
  • Muscle weakness
  • Stiff neck
  • Confusion
  • Severe headache
  • Sudden sensitivity to light.

Extreme swelling or infection at the site of the mosquito bite is another reason to get medical attention.


How is the virus spread?

West Nile virus is spread to humans by the bite of an infected mosquito.  Mosquitoes become infected by biting an infected bird.  The virus is not spread by person-to-person contact through touching or the oral or respiratory route, such as coughing, sneezing, or drinking from a shared cup.

It does not appear to be spread directly from birds to humans; however, individuals should avoid direct handling of dead birds.


How can I reduce mosquito breeding sites around my home?

The best way to start is by getting rid of places where mosquitoes can breed:

  • Don’t allow water to stand for more than 4 days (empty bird baths, tires, barrels etc.)
  • Cover rain barrels with a screen or mesh.
  • Clean gutters and eaves regularly.
  • Drill holes in bottom of containers so water can’t collect.


How can I protect myself from mosquito bites?

The best way to protect myself and my family from mosquito bites:

  • Wear light-coloured clothing
  • Wear long sleeves and pants
  • Use insect repellent with DEET.

This page provides basic information only. It must not take the place of medical advice, diagnosis or treatment. Always talk to a health care professional about any health concerns.


For Further Information

Call the Infectious Disease Program: (807) 625-5900

or toll-free 1-888-294-6630

Health Topic
Diseases & Infections