West Nile Virus - Fact sheet

West Nile Virus infection
West Nile Virus Infection is spread to people by the bite of a mosquito infected with West Nile virus. Viruses that are spread to people by mosquitoes are called arboviruses. In temperate climates, West Nile virus infections generally occur during warm weather months when mosquitoes are active.

West Nile Fever is not new
It was first identified in 1937 in Uganda, Africa. Prior to 1999, the virus had only been identified in Africa, Europe, the Middle East and Asia. West Nile virus was first detected in the United States in 1999, when at least 62 cases and seven deaths from West Nile virus were reported in the New York City area.

Anyone can get it
Anyone can get infected with West Nile virus. More severe infections are seen in the elderly and those with a weakened immune system. Most people (4 out of 5) who are infected with West Nile Virus will not develop any type of illness. However, you cannot know ahead of time if you will get sick or not if infected.

Symptoms
It usually takes two to 15 days for symptoms to appear after exposure to the infection. Symptoms of West Nile Fever generally last a few days, although even some healthy people have had the illness last for several weeks. Symptoms of Severe West Nile Disease, such as encephalitis or meningitis, may last several weeks, and neurological effects may be permanent.

People with a mild infection may experience fever, headache, eye pain, muscle aches, joint pain, a rash on the trunk and swollen lymph nodes. In severe cases symptoms include extreme muscle weakness, inflammation of the brain (encephalitis), paralysis and coma. In rare cases, the infection may be fatal, particularly in the elderly and people with other medical conditions.

Mosquitoes spread the disease
This virus is spread by the bite of a West Nile virus-infected mosquito. Mosquitoes get infected with West Nile virus by feeding on infected birds. There is no evidence that a person can acquire the virus from handling live or dead birds or other infected animals. The virus cannot be spread from one person to another.

Stop the bite to stop the spread
Preventing mosquito bites will prevent West Nile virus infection. Personal protective measures such as limiting the time spent outdoors at dawn and dusk or other times mosquitoes are active, wearing long sleeve shirts and long pants when outdoors, using insect repellents when outdoors and screening your home to prevent mosquito entry can serve to reduce or prevent mosquito bites.

Reducing mosquito populations will also reduce mosquito bites. In some communities, public funded surveillance and control programs reduce mosquito populations by eliminating mosquito breeding habitat, mosquito larvae or adults.

You can also take measures in your own yard or on your property to eliminate standing water where mosquitoes breed. Sources of standing water include old tires, metal cans, ceramic pots, clogged rain gutters, wading pools, pool covers or birdbaths.