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What is West Nile Virus?
West Nile virus (WNV) is a mosquito-borne zoonotic arbovirus belonging to the genus Flavivirus in the family Flaviviridae. West Nile virus (WNV) is most commonly transmitted to humans by mosquitoes. You can reduce your risk of being infected with WNV by using insect repellent and wearing protective clothing to prevent mosquito bites.
There are no medications to treat or vaccines to prevent WNV infection. West Nile virus (WNV) is an infectious disease that first appeared in the United States in 1999. Infected mosquitoes spread the virus that causes it. People who get West Nile Virus (WNV) usually have no symptoms or mild symptoms. The symptoms include a fever, headache, body aches, skin rash, and swollen lymph glands. They can last a few days to several weeks, and usually go away on their own.
However, some people who become infected with West Nile Virus develop a life-threatening illness that includes inflammation of the brain.
Mild signs and symptoms of a West Nile Virus infection generally go away on their own. But severe signs and symptoms such as a severe headache, fever, disorientation or sudden weakness require immediate attention.
Exposure to mosquitoes where West Nile Virus exists increases your risk of getting West Nile virus infection. Protect yourself from mosquitoes by using mosquito repellent and wearing clothing that covers your skin to reduce your risk.
Most people who get West Nile virus (70% to 80%) experience no symptoms at all. Others may experience a sudden high fever with these flu-like symptoms:
- headache
- joint pains
- vomiting
- diarrhea
- rash
The first human case of West Nile virus infection in Canada was reported in Ontario in 2002. Since then, cases have been reported so far in:
- British Columbia
- Alberta
- Saskatchewan
- Manitoba
- Ontario
- Quebec
Outside of these provinces, any reported cases have been linked to travel.
Most have no signs or symptoms
Most people infected with the West Nile virus have no signs or symptoms.
Mild infection signs and symptoms
About 20 percent of people develop a mild infection called West Nile fever. Common signs and symptoms of West Nile fever include:
- Fever
- Headache
- Body aches
- Fatigue
- Back pain
- Skin rash (occasionally)
- Swollen lymph glands (occasionally)
- Eye pain (occasionally)
Serious infection signs and symptoms
In less than 1 percent of infected people, the virus causes a serious neurological infection. Such infection may include inflammation of the brain (encephalitis) or of both the brain and surrounding membranes (meningoencephalitis). Serious infection may also include infection and inflammation of the membranes surrounding the brain and spinal cord (meningitis), inflammation of the spinal cord (West Nile poliomyelitis) and acute flaccid paralysis a sudden weakness in your arms, legs or breathing muscles. Signs and symptoms of these diseases include:
- High fever
- Severe headache
- Stiff neck
- Disorientation or confusion
- Stupor or coma
- Tremors or muscle jerking
- Lack of coordination
- Convulsions
- Pain
- Partial paralysis or sudden muscle weakness
Signs and symptoms of West Nile fever usually last a few days, but signs and symptoms of encephalitis or meningitis can linger for weeks, and certain neurological effects, such as muscle weakness, may be permanent.
West Nile Virus Treatment
West Nile virus causes an infection that can lead to inflammation of the brain (encephalitis), the spinal cord (myelitis), or the tissues surrounding it and the spinal cord (meningitis). No specific treatment is available. Mild infections go away on their own. Severe cases of encephalitis are treated with supportive care in a hospital. Supportive care involves helping the body fight illness on its own. It often is used when no specific treatment exists for an illness, as is the case with some viruses.
Supportive treatment for West Nile virus can include receiving fluids through a vein (intravenous, or IV), help with breathing (using a ventilator), and prevention of secondary infections, such as pneumonia. Medicine may also be used to relieve pain or a fever.
