Infectious Disease Epidemiology Program

Questions: West Nile Virus

West Nile Virus FAQs (Word* | also in PDF*)

  1. What is West Nile virus?
    1. A. West Nile virus is a potential serious disease caused by the bite of an infected mosquito.  West Nile virus can infect humans, birds, mosquitoes, horses and some other mammals.

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  2. When was West Nile virus first found in the United States?
    1. A. West Nile virus was first identified in New York City in 1999. West Nile virus was first detected in Maine in a bird in 2001. 

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  3. How is West Nile virus spread to humans?
    1. A. West Nile virus is normally spread to humans by the bite of a mosquito that already has the virus. In a very small number of cases, West Nile virus also has been spread through blood transfusions, organ transplants, breastfeeding and during pregnancy from mother to baby.

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  4. Who is at risk of getting West Nile virus?
    1. A. All residents of Maine, especially those in areas where virus activity has been identified in recent years, can be infected with West Nile virus. People over 50 years of age have the highest risk of severe disease, if bitten by a mosquito that has the virus. However, please note not all mosquitoes can spread West Nile virus.

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  5. What are some of the signs of West Nile virus infection?
    1. A. Most West Nile virus infections do not cause any symptoms. Mild West Nile virus infections can cause fever, headache and body aches, often with a skin rash and swollen lymph glands. In a small percentage of people infected by the virus, the disease can be serious, with additional complications such as neck stiffness, stupor, disorientation, coma, tremors, convulsions, paralysis and, sometimes, death.

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  6. How soon do signs of West Nile virus infection appear?
    1. A. Signs for West Nile virus infection begin to appear 5 to 15 days after infection.

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  7. How is West Nile virus infection diagnosed?
    1. A. West Nile virus infection can only be diagnosed by a doctor. If you think you have any of the signs above, you should make an appointment to see your doctor as soon as you can. If your doctor suspects that you may have West Nile virus infection, he or she will take your blood sample and draw a special fluid from your spinal cord (cerebral spinal fluid). Your doctor will then send these samples to the Maine Health and Environmental Testing Laboratory for specific tests to be done to see if you have West Nile virus.

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  8. What is the treatment for West Nile virus infection?
    1. A. There is no specific treatment for West Nile virus infection. People with mild West Nile virus infections usually recover on their own. Physicians can provide supportive therapy for people who have more serious complications, such as encephalitis or meningitis.

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  9. Is there a vaccine I can get for West Nile virus?
    1. A. Currently, there is no vaccine available for West Nile virus.

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  10. I’ve heard that West Nile virus can be spread through blood transfusions or organ transplants. What is the Maine CDC doing about testing people before they donate blood?
    1. A. Some people have developed West Nile virus after receiving a transplanted organ or blood products from an infected donor. Since 2003, blood donor agencies such as the American Red Cross have screened people for West Nile virus after blood donation and before blood transfusions. Unfortunately, there is currently no federally mandated law requiring that donated organs get screened for West Nile virus.

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  11. What time of the year am I most likely to get West Nile virus?
    1. A. People are at the highest risk of being infected with West Nile virus between the months of May and October.

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  12. How can I protect myself and my family from getting infected with West Nile virus?
    1. A. You can protect yourself and your family from West Nile virus and other mosquito-borne viruses by taking the following actions:
      1. Use insect repellent that contain DEET
      2. Wear long-sleeved shirts, pants and socks when outdoors
      3. Install or repair window screens
      4. Avoid being outdoors at dawn or dusk
      5. Drain standing water
    2. More information about personal protection can be found by going to the federal CDC website External site disclaimer

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  13. Do all mosquitoes spread West Nile virus?
    1. A. No. Not all mosquitoes spread West Nile virus.

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  14. Where do mosquitoes live and breed?
    1. A. Mosquitoes lay their eggs in moist areas, such as standing water. The eggs become larvae that remain in the water until the adults mature and fly off. Weeds, tall grass, and shrubs provide an outdoor home for adult mosquitoes. They can also enter houses through unscreened windows or doors, or broken screens. Many mosquitoes will breed in containers that hold water, such as flowerpots or discarded tires.

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  15. How can I reduce the number of mosquitos around my home and my neighborhood?
    1. A. To reduce mosquito populations around your home and neighborhood, get rid of any standing water that is available for mosquito breeding. Mosquitoes will begin to breed in any puddle or standing water that lasts for more than four days. Here are some simple steps you can take:
      • Get rid of or regularly empty any metal cans, plastic containers, ceramic pots, and other water holding containers (including trash cans) on your property.
      • Pay special attention to discarded tires that may have collected on your property. Stagnant water in tires is a common place for mosquitoes to breed.
      • Drill holes in the bottom of recycling containers that are left outdoors, so that water can drain out.
      • Clean clogged roof gutters; remove leaves and debris that may prevent drainage of rainwater.
      • Turn over plastic wading pools and wheelbarrows when not in use.
      • Do not allow water to stagnate in birdbaths; aerate ornamental ponds or stock them with fish.
      • Keep swimming pools clean and properly chlorinated; remove standing water from pool covers.
      • Use landscaping to eliminate standing water that collects on your property.

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  16. Can my pet be infected?
    1. A. If you have any questions about the health of your pet or other domestic animals you should call the state veterinarian at the Department of Agriculture at (207)287-7613 or (207)287-7615.

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  17. What is the Maine CDC doing to protect residents from West Nile virus infection?
    1. A. Maine CDC has developed a surveillance system to track the occurrence of West Nile virus and other arboviruses, generally beginning in July and lasting through the end of September. Surveillance efforts include adult mosquito trapping and testing, testing of animals including llamas, alpacas, and horses, and testing people who are ill with symptoms similar to those of an arbovirus infection. In addition, the Maine CDC has been collaborating with other state agencies, health professionals and non-governmental groups to work together since 2000 to increase awareness and promote preventive measures.

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