West Nile Virus

What is West Nile virus?

West Nile virus (WNV) is a mosquito transmitted virus that can be transferred to humans from the bite of an infected mosquito. The first confirmed case in Canada was in 2002.  

How is West Nile virus spread?

Mosquitoes become infected with WNV when they feed on infected birds. The bite by an infected mosquito can then transmit WNV to humans and other animals. The virus is not known to spread through touching, kissing, or caring for someone who is infected.  In very rare cases, WNV can be spread through blood transfusion, organ or tissue transplants, during pregnancy from mother to baby, breast milk, or exposure of laboratory workers to infected medical specimens.

Who is at risk for West Nile virus?

People of all ages can be infected with West Nile virus. The risk of severe illness increases with age and is greater for people with chronic diseases or weakened immune systems.

What are the symptoms of West Nile virus?

No Symptoms

Most people (70-80%) who get WNV will not get sick or experience any symptoms.

Mild Symptoms

Almost 20% of those infected will have West Nile fever, which consists of fever, headache, body aches, swollen lymph nodes, and mild rash. These symptoms can last for as short as a few days to as long as several weeks.

Severe Symptoms

Very few people will develop severe symptoms that affect the central nervous system. These include:  quick onset of severe headache, high fever, muscle weakness, stiff neck, vomiting, confusion, paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

If you experience sudden onset of any of the symptoms listed above, seek medical attention immediately. While there is no treatment or vaccine for WNV, symptoms can be treated.

How can I protect myself and my family from West Nile Virus?

The best way to avoid WNV is by not being bitten by mosquitoes. For more detailed information on protection please refer to our web pages on Mosquito Safety.

Will I be kept informed?

The Windsor-Essex County Health Unit will keep you informed about West Nile virus through media releases, pesticide use notices posted in local papers, the Health Unit’s website, social media, and the distribution of information at locations throughout the county.

For more information:

Speak with a Public Health Inspector by calling 519-258-2146 ext. 4475, or visit canada.ca and search ‘West Nile virus’.

Key References:

Diagnosis is based on clinical presentation and serological test results.  For further information about testing, please contact Public Health Ontario Laboratory Services, toll free: 1-877-604-4567

West Nile Virus case definition 

Ontario’s Public Health Infectious Disease Protocol/Management 

Government of Canada. (2016). West Nile Virus. Retrieved from https://www.canada.ca/en/public-health/services/diseases/west-nile-virus.html

Centers for Disease Control and Prevention. (2016). West Nile Virus. Retrieved from https://www.cdc.gov/westnile/

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