Published on March 8, 2024 at 8:00 / Updated on March 26, 2024 at 8:00

The West Nile Virus (WNV) is a disease transmitted through the bite of an infected mosquito. First identified in the West Nile region of Africa, the virus appeared in North America in 1999, and can therefore now be contracted in Canada.

Most people infected with the WNV do not have any symptoms. Others, however, can develop the following symptoms:

  • Headache
  • Fever
  • Gastrointestinal symptoms
  • Muscle weakness
  • Redness and rash
  • Neck stiffness
  • Disorientation or confusion

In rare cases (less than 1% of those infected with WNV), serious complications can occur. These include meningitis (an infection of the membranes that cover the brain), encephalitis (an inflammation of the brain) and paralysis of the lower limbs.

Causes and triggers

Generally speaking, WNV is transmitted to humans via infected mosquitos (mosquitoes become infected when they feed on infected birds). WNV cannot be transmitted through person-to-person contact and there is no evidence that it can be transmitted by handling an infected animal.

While anyone can contract WNV, those who spend a great deal of time outside are most at risk. Serious complications of WNV most often affect adults over 50 years of age and those with chronic diseases (e.g., diabetes, heart disease) and weakened immune systems.


There is no specific treatment or vaccine for WNV infection in humans. However, most of those who are infected recover without treatment. Over-the-counter pain relievers may be used to manage symptoms and reduce discomfort. When complications occur, hospitalization may be required to stabilize and improve the patient's health status.

The most effective way to protect yourself from becoming infected is to prevent mosquito bites:

  • Cover skin as much as possible
    • Wear long, loose-fitting clothing
    • Wear socks and a hat
    • Wear light-coloured clothing (mosquitoes are attracted to dark colours)
  • Use insect repellent (bug spray) that contains DEET or icaridin
  • Get rid of standing water (water that does not move or flow) around the house since this is where mosquitoes lay their eggs

Also, handling dead animals or birds with bare hands is not advised.

When should I see a healthcare professional?

See a healthcare provider right away if you have the following symptoms:

  • Rapid onset of severe headache
  • High fever
  • Stiff neck
  • Muscle weakness
  • Nausea and vomiting
  • Difficulty swallowing
  • Drowsiness or confusion
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