Healthy places Environmental health hazards West Nile virus About West Nile virus

About West Nile virus


What is West Nile virus?

West Nile virus (WNV) is a virus mainly transmitted to people through the bite of an infected mosquito. It was first identified in North America in 1999.

How does WNV infect people?

WNV is spread to humans and animals through the bite of an infected mosquito. Mosquitoes get the virus by feeding on infected birds.

The virus is not transmitted from person-to-person. Although animals such as dogs, cats and horses can become infected from an infected mosquito, there is no evidence of animal-to-animal, or animal-to-human transmission of this virus. There is also no evidence of infection from handling infected birds; however, you should avoid handling any dead animal with bare hands.

What are the symptoms of WNV?

Most people who are infected with WNV have no symptoms at all, or have a mild illness such as fever, headache, muscle weakness, and body aches. This is now called West Nile Virus Non-Neurological Syndrome (WNV Non-NS)

Symptoms may appear 2-15 days after being bitten by an infected mosquito. A few people will experience a more severe form of WNV, called encephalitis (swelling of the brain). Symptoms of encephalitis may include a rapid onset of severe headache, high fever, stiff neck, and disorientation. The elderly and young children are at a greater risk for severe disease, due to weak or less developed immune systems.

What is the treatment for West Nile infection?

There is no specific treatment for WNV infection. Antibiotics are not effective and there is no WNV vaccine approved for human use at this time. It is, therefore, very important to protect yourself against mosquito bites.

More information

WNV in Oxford County
Government of Ontario – Public Information: West Nile virus
Health Canada – It’s Your Health: WNV fact sheet