West Nile Virus

West Nile virus is a potentially serious illness, a seasonal epidemic in North America that flares up in the summer and continues into the fall. This fact sheet from the Centers for Disease Control contains important information that can help you recognize and prevent West Nile virus.

What Can I Do to Prevent West Nile Virus?
The easiest and best way to avoid West Nile virus is to prevent mosquito bites.

• When outdoors, use insect repellents containing an EPA-registered insect repellent and follow the directions on the package.

• Many mosquitoes are most active at dusk and dawn. Use insect repellent, wear long sleeves and pants, or consider staying indoors during these hours.

• Make sure you have good screens on your windows and doors to keep mosquitoes out.

• Get rid of mosquito breeding sites.
  Empty standing water from flower pots, buckets, and barrels.
  Change the water in pet dishes regularly.
  Replace the water in bird baths weekly.
  Drill holes in tire swings so water drains out.
  Keep children’s wading pools empty and on their sides when not used.

Serious Symptoms in a Few People
About one in 150 people infected with West Nile virus will develop severe illness.

The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

Milder Symptoms in Some People
Up to 20 percent of the people who become infected will display symptoms which can include fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have been sick for several weeks.

No Symptoms in Most People
Approximately 80 percent of people (about 4 out of 5) who are infected with West Nile virus will not show any symptoms at all, but there is no way to know in advance if you will develop an illness or not.

How Does West Nile Virus Spread?

• Infected Mosquitoes
  Most often, West Nile virus is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread the disease to humans and other animals when they bite.

• Transfusions, Transplants, and Mother-to-Child
  In a very small number of cases, West Nile virus also has been spread through blood transfusions, organ transplants, breastfeeding, and even during pregnancy from mother to baby.

• Not Through Touching
  West Nile virus is not spread through casual contact such as touching or kissing a person with the virus.

How Soon Do Infected People Get Sick?
People typically develop symptoms between 3 and 14 days after they are bitten by the infected mosquito.

How Is Infection Treated?
There is no specific treatment for West Nile virus infection.

In cases with milder symptoms, people experience symptoms like fever and aches that pass on their own, although illness may last for weeks or months, even in healthy people.

In more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing, and nursing care.

What Should I Do If I Think I Have West Nile Virus?
Milder West Nile virus illness improves on its own, and people do not necessarily need to seek medical attention for this infection, though they may choose to do so.

If you develop symptoms of severe West Nile virus illness, such as unusually severe headaches or confusion, seek medical attention immediately. Severe West Nile virus illness usually requires hospitalization.

Pregnant women and nursing mothers are encouraged to talk to their doctor if they develop symptoms that could be West Nile virus.

What Is the Risk of Getting Sick from West Nile Virus?

• People over the age of 50 are more likely to develop serious symptoms if they do get sick and should take special care to avoid mosquito bites.

• Being outside means you’re at risk. The more time you’re outdoors, the more time you could be bitten by an infected mosquito. Pay attention to avoiding mosquito bites if you spend a lot of time outside, either working or playing.

• Risk through medical procedures is very low. All donated blood is checked for West Nile virus before being used. The risk of getting West Nile virus through blood transfusions and organ transplants is very small, and should not prevent people who need surgery from having it. If you have concerns, talk to your doctor.

• Pregnancy and nursing do not increase risk of becoming infected with West Nile virus. The risk that West Nile virus may present to a fetus or an infant infected through breastmilk is still being evaluated. Talk with your healthcare provider if you have concerns.

What Else Should I Know?
If you find a dead bird, don’t handle the body with your bare hands. Contact your local health department for instructions on reporting and disposing of the body. They might tell you to dispose of the bird after they log your report.

For more information, visit www.cdc.gov/westnile, or call CDC at 800-CDC-INFO (English and Spanish) or 888-232-6348 (TTY).