Environmental Health
West Nile Virus Fact Sheet
The West Nile Virus (WNV) infects certain wild
birds. Infected WNV mosquitoes bite a bird and the bird serves as a
host for the virus. Mosquitoes become infected when they feed on
infected birds. Infected mosquitoes can transmit WNV to humans.
Q. What is West Nile virus encephalitis?
A . West Nile virus encephalitis is a mosquito-borne viral disease, which can cause an inflammation of the brain. The West Nile virus (WNV) is commonly found in Africa, West Asia, the Middle East and Europe, and is closely related to St. Louis encephalitis virus, which was found in New Jersey in 1964 and 1975. For the first time in North America, WNV was confirmed to be present in the New York metropolitan area during the summer and fall of 1999.
Q. How is West Nile virus spread?
A. West Nile virus is spread to humans by the bite of an infected mosquito. A mosquito becomes infected by biting a bird that carries the virus. The virus is NOT spread by person-to-person contact and cannot be spread directly from birds to people. (Note: dead birds should still not be handled with bare hands).
Q. What are the symptoms of West Nile virus infection?
A. Most infections produce no symptoms in people, or are mild or moderate. Symptoms may include: fever, headache, and body aches, often with skin rash and swollen lymph glands. More severe infections may be marked by headache, high fever, neck stiffness, muscle weakness, stupor, disorientation, convulsions, paralysis, coma, and rarely, death.
Q. Who is most at risk?
A . People over 50 years of age have the highest risk of developing a severe illness because as we age, our bodies have a harder time fighting off disease. People with compromised immune systems are also at increased risk, however, anyone can get the virus.
Q. Is there a vaccine against West Nile virus?
A. No. A vaccine for West Nile virus does not exist.
Q. How long does it take to get sick if bitten by an infected mosquito?
A. Being bitten by an infected mosquito will not necessarily make you sick since most people who are infected with West Nile virus have no symptoms or experience only mild illness. If illness were to occur, it would occur within 3 to 15 days of being bitten by an infected mosquito.
Q. What should I do if I think I have West Nile encephalitis?
A. If you develop signs of encephalitis, with fever, muscle weakness, and confusion, you should seek medical care as soon as possible.
Q. I've gotten a mosquito bite. Should I be tested for West Nile virus?
A. No. Most mosquitoes are not infected with the West Nile virus. However, you should see a doctor immediately if you develop symptoms such as high fever, confusion, muscle weakness, severe headaches, stiff neck, or if your eyes become sensitive to light. Patients with mild symptoms should recover completely, and do not require any specific medication or laboratory testing.
Q. If I live in an area where birds or mosquitoes with West Nile virus have been reported, and I am bitten by a mosquito, am I likely to get sick?
A . No. Even in areas where mosquitoes do carry the virus, very few mosquitoes -- less than 1 % -- are infected. The chances that any one bite will be from an infected mosquito are very small.
Q. Can you get West Nile virus from an infected person?
A . You cannot get West Nile virus from a person who has the disease. West Nile virus is not spread by person-to-person contact such as touching, kissing, or caring for someone who is infected.
Q. Can you get West Nile virus directly from birds?
A . There is currently no evidence that West Nile virus can be spread directly from birds to people. However, dead birds can carry a variety of diseases and, therefore, should never be handled with bare hands. Use gloves to carefully place dead birds in double-plastic bags and then place dead birds in the outdoor trash.
Q. Besides mosquitoes, can you get West Nile virus directly from other insects or ticks?
A . Infected mosquitoes are the primary source of West Nile virus and caused the outbreaks throughout the United States. There is no information to suggest that ticks or other insects transmit West Nile virus.
What can you do to protect yourself?
The best way to protect yourself is to keep mosquitoes from biting you. During mosquito season (generally April through October), take the following precautions:
- Limit outdoor activities between dusk and dawn, if possible, since this is the time of greatest mosquito activity.
- If you are outside when mosquitoes are prevalent, wear protective clothing such as long pants, long-sleeved shirts, and socks.
- Use a mosquito repellant that contains DEET (the chemical N-N-diethyl-meta-toluamide) and follow the directions on the label.
What can I do around my home to help reduce exposure to mosquitoes?
- Dispose of, regularly empty, or turn over any water holding containers on your property such as tires, cans, flowerpots, or trashcans.
- Drill holes in the bottom of recycling containers that are left outdoors.
- Make sure roof gutters drain properly and water doesn't stand in them.
- Change the water in birdbaths at least once a week.
- Turn over plastic wading pools and wheelbarrows when not in use.
- Keep swimming pools, outdoor saunas, and hot tubs clean and properly chlorinated; remove standing water from pool covers.
- Eliminate any standing water that collects on your property.
- Remind or help neighbors to eliminate mosquito-breeding sites.
- Fix any holes in your screens and make sure they are tightly attached.
Q. Does a dead bird in my community mean WNV is in the area?
A. An increase in deaths in crows and blue jays can be an indication of WNV circulating in an area. However, risk to humans will be very low since less than 1% of mosquitoes will be able to transmit the virus; and less than 1% of people who get bitten by a mosquito and become infected will get severely ill.
Q. What should I do if I find a dead crow or blue jay?
A. If you notice a freshly dead crow or blue jay , you should contact your local health department's environmental or vector control section to see about testing. To keep it from deteriorating in the heat, you should place it in a plastic bag (hand in bag, grasp bird, pull bag over hand), double bag and refrigerate, or keep on ice until delivered to the Health Department. Not every bird reported will be submitted for testing, especially after WNV is already known to be in the area.
1. Ensure the dead bird fits these criteria:
- American crows or blue jays found in Tennessee
- Less than 24 hours since death
- No odor or maggots ( Indicates tissue decomposition)
- Is an intact bird (whole bird)
American Crow: Tip of bill to tip of tail is 15 -17 inches.
Blue Jay: Tip of bill to tip of tail is 9-11 inches.
2. Wear gloves while handling the carcass (as is prudent for handling any dead wild animal). If gloves are not available, a plastic bag can be placed over one's hand, the bird picked up, and the bag pulled over the carcass.
3. Double-bag the carcass in a resealable clear storage bag or other clear plastic bag so that the bird can be clearly seen through the bag.
4. Keep the carcass in a disposable cooler or utility refrigerator. Keeping the bird cool will slow tissue decomposition. The cooler should be kept out of the sun.
5. The following information will need to be supplied to the county health department upon submission of the carcass:
- a. Name and phone number of the person submitting the bird.
- b. Location of where the bird was found: street address, city or town, county, zip code.
- c. Type of bird (American crow or blue jay) and date the bird was found.
