West Nile

West Nile virus (WNV) can cause a fatal neurological disease in people who are bitten by an infected mosquito.

Areas of risk

West Nile virus is found in Africa, Europe, the Middle East, North America, and Western Asia

Key facts

Mosquitoes become infected when they feed on birds infected with WNV.

These mosquitoes then spread the virus to people and other animals.

According to several serosurveys conducted in Canada, the estimated rate of human exposure to WNV is 3%–5%.

prevention guidance

In total, 5,454 cases of WNV disease were reported to the Public Health Agency of Canada between 2002 and 2013, including 1,072 cases of WNV neurological disease.

West Nile at a glance

Primary vector


Biting habits:

  • Evening to morning


80% of people infected with WNV are asymptomatic (no symptoms)

About 20% of people who become infected with WNV will develop West Nile fever.

Symptoms include:

  • Headache
  • Body aches
  • Joint pain
  • Vomiting
  • Diarrhea
  • Rash

Symptoms of severe disease include:

  • High fever
  • Headache
  • Neck stiffness
  • Stupor
  • Disorientation
  • Coma
  • Tremors
  • Convulsions
  • Muscle weakness
  • Vision loss
  • Numbness
  • Paralysis

Severe West Nile virus

~1 in 150

people who are infected develop severe symptoms affecting the central nervous system

Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk for severe illness if they are infected. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.

~1 in 10

people with disease affecting the central nervous system die

Help reduce the risk of mosquito-borne diseases dampening your travel experience. Learn more by speaking to your healthcare professional, such as a doctor or pharmacist, or visiting a travel clinic, before your next trip.