Frequently Asked Questions about West Nile Virus

West Nile Virus in People

Q1. What is West Nile virus?
Q2. How is West Nile virus spread to persons?
Q3. Can West Nile virus be spread in blood transfusions or organ transplants?
Q4. Can West Nile virus be spread during pregnancy or in breast milk?
Q5. Who is most at risk?
Q6. What are the symptoms of West Nile virus?
Q7. Are there long-term effects of West Nile virus?
Q8. Can West Nile virus be treated?
Q9. Is there a vaccine for West Nile virus?
Q10. How is a person tested for West Nile virus?
Q11. How can West Nile virus be prevented?

Q1. What is West Nile virus?

West Nile virus is a member of the virus family Flaviviridae. It is closely related to several other viruses that are transmitted by mosquitoes which can cause illness in persons, for example St. Louis encephalitis and Dengue fever.

Q2. How is West Nile virus spread to persons?

West Nile virus is usually spread to persons by the bite of an infected mosquito. Mosquitoes become infected by feeding on a bird that carries the virus in its blood. Additional routes of spread were discovered in 2002. These methods are extremely rare and include blood transfusions, organ transplants, and spread from mothers to their children in breast milk or through the womb.

Q3. Can West Nile virus be spread in blood transfusions or organ transplants?

In 2002, there were a few confirmed cases of spread of West Nile virus from transfusion of blood products or organ transplants. The risk of getting West Nile virus through these procedures is considered very low. Although persons needing blood transfusions or organ transplants should be aware of the risk of West Nile virus infection, the benefits of receiving needed transfusions or transplants far outweigh the potential risk for West Nile virus infections.

Blood is lifesaving. Donating blood is safe and blood donation is encouraged now and in the future. Canadian Blood Services has implemented a screening test to find West Nile virus in donated blood (July 1, 2003). Public Health officials continue to work with the Canadian Blood Service to protect the blood supply, by identifying West Nile virus infections in persons who may have recently donated blood or received blood or blood products.

Q4. Can West Nile virus be spread during pregnancy or in breast milk?

In 2002, there was evidence that spread of West Nile virus from mothers to their children during pregnancy and in breast milk is possible. It is important for pregnant and breast-feeding women to reduce their risk of exposure to mosquitoes. Women who have concerns about this issue should consult their doctor.

Q5. Who is most at risk?

Anyone exposed to mosquitoes in an area where West Nile virus has been detected is at some degree of risk of infection. The risk of serious health effects from the virus is very low for healthy persons with a good immune system.

While persons of any age or health status can be at risk for serious health effects associated with West Nile virus, the overall risk of serious health effects increases with age. Persons with weaker immune systems and persons with chronic diseases are at greater risk for serious health effects.

Q6. What are the symptoms of West Nile virus?

Most persons who become infected with West Nile virus have no symptoms at all, or they may experience mild flu-like symptoms that usually appear two to fifteen days after infection. Mild symptoms could include fever, headache and body aches, a mild rash, or swollen lymph glands. Most persons who become ill recover.

Some individuals have weaker immune systems, and they are at greater risk for serious health effects, including encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain). In such cases, symptoms may include severe headache, high fever, stiff neck, vomiting, drowsiness, confusion, muscle weakness, other evidence of brain involvement, loss of consciousness, or even death.

Q7. Are there long-term effects of West Nile virus?

West Nile virus is an emerging disease. The long-term effects are not fully understood. Studies to date show that some persons with serious health effects recover completely while others experience prolonged health problems. This includes physical effects, cognitive effects, and functional effects.

Q8. Can West Nile virus be treated?

There is no specific treatment, medication or cure. In serious cases, symptoms and complications of the disease can be treated. Most persons who get this illness recover from it.

Q9. Is there a vaccine for West Nile virus?

At this time there is no vaccine to protect persons against West Nile virus.

Q10. How is a person tested for West Nile virus?

Your physician will first assess your medical history and your symptoms of illness. If necessary, a blood or other sample can be taken and sent to a laboratory for testing.

Q11. How can West Nile virus be prevented?

Prevent exposure to mosquito bites. Make sure door and window screens fit tightly. Minimize time spent outdoors at dawn and dusk when mosquitoes are most active. Wear light-coloured clothing, long-sleeved tops, long pants, and socks. Use an insect repellent containing DEET or other approved ingredients. Reduce mosquito populations around your home and property by eliminating mosquito breeding sites of standing pools of water (for example, empty wading pools, remove old tires, clean rain gutters regularly).