West Nile Virus

Transmission and Symptoms

How would I get WNV?

Humans can get WNV from the bite of a mosquito that is carrying the virus or through blood transfusions or organ donations from an infected donor. You cannot get WNV from donating your blood. There is also the possibility that the virus can be passed from pregnant mothers to unborn children. WNV may be passed through breast milk, but mothers are still encouraged to breastfeed their babies. In the majority of cases, WNV is spread by the bite of an infected mosquito.

Can I get WNV directly from birds?

There is no evidence that a person can get the virus by handling live or dead infected birds. However, it is important to wear gloves when handling any dead animal and wash hands thoroughly with soap and hot water after removing gloves.

Is WNV infection serious?

Most people who are infected do not get sick at all. Some people who are infected may develop a mild illness, with fever and body aches. Less than 1% of people who get bitten and become infected will get severely ill. The elderly are at greatest risk for serious illness.

What are symptoms of West Nile virus?

Most people who are infected have no symptoms. Some people may have fever, headache, nausea, body aches, or other symptoms. Very rarely the disease may progress to encephalitis which may cause severe headache, confusion, weakness, or dizziness. The time between a mosquito bite and onset of illness ranges from 3 to 14 days in humans.

What should I do if I think I may have symptoms of West Nile virus?

Call your health care provider if you have concerns about your health. See your provider immediately if you or your family members develop symptoms such as high fever, confusion, muscle weakness, and severe headaches. Tell your provider if you have been active outdoors or have recent mosquito bites.

Does West Nile virus affect dogs, cats, or horses?

There is a very low infection rate in dogs and cats. WNV causes illness and deaths in horses. WNV vaccine for horses is available. If you are concerned, contact your veterinarian.

Page updated March 05, 2008