West Nile Virus
What is West Nile virus?
West Nile virus (WNV) is a virus carried by mosquitoes.
Most people infected with the virus do not have symptoms or have only a mild illness.
Less than 1 in 100 people who are infected with the virus develop serious illness.
Serious forms of illness caused by WNV include encephalitis (inflammation of the brain) or meningitis (inflammation of membranes that cover the brain and spinal cord).
How does it occur?
Wild and domestic birds, mainly crows, carry West Nile virus.
Mosquitoes become carriers of the virus when they bite infected birds.
Humans can get the virus when they are bitten by infected mosquitoes. There are no known cases of a human getting WNV from an infected bird, only a bite from an infected mosquito.
The West Nile virus season in Canada is from May to October. The peak time for infection is mid to late August.
The risk of severe infection is greatest for people with chronic illnesses or those who have a weakened immune system.
West Nile virus may spread from person to person through blood transfusions and organ transplants.
The virus might also be transmitted through breast milk. However, the risk of transmission of the virus to the baby is believed to be very low. If you are breast-feeding and you have signs and symptoms of WNV infection, you should see your healthcare provider for advice.
The infection is not spread by normal person-to-person contact like touching, kissing, or caring for someone who is infected.
What are the symptoms?
About 4 out of 5 people have no symptoms.
Children are more likely to have symptoms.
When symptoms do occur, they are usually mild and last a few days.
Symptoms of WNV infection may include:
· Muscle aches
· Skin rash
· Swollen lymph glands
A WNV infection usually does not involve the brain. However, a few infected adults (and even fewer children) develop encephalitis or meningitis. Symptoms of these less common but severe illnesses include:
· Stiff neck
· Severe headache
· Muscle weakness
Some people develop a polio like syndrome with sudden weakness and paralysis. Symptoms usually appear 2 to 15 days after you were bitten by an infected mosquito.
How is it diagnosed?
Your healthcare provider will ask about your symptoms and examine you.
Tests you may have are:
· Blood tests
· Spinal tap (lumbar puncture), a procedure in which a needle is inserted between two bones of the spine into the spinal canal to take a sample of spinal fluid to test for meningitis
· Electroencephalogram (EEG), a test that measures the electrical activity of the brain (brain waves)
· Computerized tomography (CT) or magnetic resonance imaging (MRI) scans.
How is it treated?
There is no specific medicine to treat West Nile virus.
If you have a serious infection, you may need to stay at the hospital.
You may be given intravenous (IV) fluids and pain relievers.
For severe or life-threatening infection, you may need treatment in an intensive care unit.
How long will the effects last?
Most people infected with WNV, including nearly all children, do not get seriously ill, and they recover fully.
If you have a serious infection, you may be ill for weeks. You may have some injury to the nervous system and brain. The injury is sometimes permanent.
If you get West Nile virus, you will probably be immune to future infection by the virus, but your immunity might decrease over time.
How can I take care of myself?
· Take acetaminophen (Tylenol) or an anti-inflammatory medicine such as ibuprofen if you are having a fever, headache, or muscle aches.
See your healthcare provider right away if you develop:
· A stiff neck
· A headache that is getting worse
· A fever of 102°F (39°F) or higher that does not go down with medicine.
· Seizures (convulsions)
· Slurred speech
· Paralysis (inability to use an arm or leg)
If you are older or live alone, you may need someone to be checking on you often to make sure your symptoms are not getting worse in ways you may not realize, such as confusion or coma.
Can West Nile virus infection be prevented?
Yes, WNV can be prevented.
Take precautions to avoid exposure to mosquitoes:
· Stay indoors at dawn, dusk, and in the early evening, when mosquitoes are most likely to be around.
· Wear long-sleeved shirts and long pants when outdoors.
· Use an insect repellent on skin that is not covered by clothing whenever you are outdoors.
· Do not use more repellent than recommended in the package directions
· Do not put repellent on open wounds or rashes
· Do not apply it to your eyes or mouth
· When using sprays, do not spray directly on your face—spray the repellent on your hands first and then put it on your face.
· Wash the spray off your hands
· Be careful with children because repellents can make them ill
· Repellent products containing DEET as active ingredients have been proven to provide longer lasting protection than others.
· Oil of lemon eucalyptus, a plant-based repellent, hasn’t been as well tested. But in some studies it provided as much protection as repellents with low concentrations of DEET.
· Please follow your healthcare providers instructions
· Mosquitoes lay eggs in water
· To reduce breeding, drain standing water
· Routinely empty water from flowerpots, pet bowls, clogged rain gutters, swimming pool covers, buckets, barrels, cans, and other items that collect water.
Note: Vitamin B and ultrasonic devices DO NOT help prevent mosquito bites.
A vaccine is available to protect horses from West Nile virus.
No vaccine is available for humans yet, but several companies are working to develop a human vaccine.
For more information
Nova Scotia Department of Health and Wellness:
Prince Edward Island: