West Nile Virus
West Nile Virus (WNV) is a mosquito borne virus that can infect humans, birds, horses and other mammals. You can reduce your risk of being infected with WNV by using insect repellent and wearing protective clothing to prevent mosquito bites. There are no medications to treat or vaccines to prevent WNV infection. Fortunately, most people infected with WNV will have no symptoms. About 1 in 5 people who are infected will develop a fever with other symptoms. Less than 1% of infected people develop a serious, sometimes fatal, neurologic illness.
What Are The Symptoms Of The West Nile Virus?
Most people who are infected with WNV either have no symptoms (80%) or experience a mild or moderate illness with symptoms such as fever, headache, fatigue, or body aches before fully recovering. It is estimated that 20% of people who become infected with WNV will develop West Nile Fever. Of these, 1/150 persons may develop the more serious neuroinvasive West Nile.
Some persons may also develop a rash or swollen lymph glands. In some individuals, particularly persons 50 years of age and older, WNV can cause serious brain and spinal tissue damage. Severe illness may include encephalitis (inflammation of the brain), meningitis (inflammation of the membrane around the brain and spinal cord), or acute flaccid paralysis (a polio-like syndrome in which muscles become very weak or paralyzed). Other severe symptoms may include headache, high fever, stiff neck, nausea and vomiting, confusion, coma, tremors, convulsions, muscle weakness and/or paralysis. At its most serious, WNV can cause permanent neurological damage and death. Among those people who need to be hospitalized for WNV, 10-15% die of their illness. People who do develop symptoms normally become ill 3-15 days following the bite of an infected mosquito.
How Is West Nile Virus Spread?
- Infected Mosquitoes. Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.
- Transfusions, Transplants, and Mother-to-Child. In a very small number of cases, WNV also has been spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby.
- Not through touching. WNV is not spread through casual contact such as touching or kissing a person with the virus.

Can you get West Nile Virus directly from birds?
There is no evidence that a person can get the virus from handling live or dead infected birds. However, persons should avoid bare-handed contact when handling any dead animals and use gloves or double plastic bags to place the carcass in a garbage can.
How is West Nile Virus treated?
There is no specific treatment for WNV. Most people who become infected will get better on their own. In more severe cases, intensive supportive therapy is indicated, i.e., hospitalization, intravenous (IV) fluids and nutrition, airway management, ventilator support if needed, prevention of secondary infections and proper nursing care.
How long does it take to get sick if bitten by an infected mosquito?
Most people who are infected with WNV have no symptoms or experience only mild illness. If illness does occur, symptoms generally appear between 3 to 15 days of being bitten by an infected mosquito.