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West Nile Virus

Insect repellent on child

Don’t let mosquitoes wreck your summer fun. Protect yourself and your family from mosquito bites.

Summertime means mosquitoes and West Nile virus season. An infected mosquito bite can make you or a family member sick with West Nile virus. Stay healthy this summer. Avoid mosquito bites, especially from dusk (evening) to dawn (morning) when the mosquitoes that spread West Nile virus are most active.

How many people get sick with West Nile virus?

Nearly 42,000 cases of West Nile virus disease have been reported in the United States since 1999. Of those, nearly 19,000 people have had neurologic disease (infections of the brain or spinal cord) and more than 1,700 people have died. Many more cases of illness are not reported to CDC. Since 1999, an estimated 700,000 people in the United States have become ill due to West Nile virus infection.

What are the risks?

Figure 1. West Nile virus activity by state in the United States, 2015. View Map.

See detailed case counts by state for 2015.

All 48 states in the continental United States have had human West Nile virus disease cases (see figures 1 and 2 for states with West Nile virus activity in 2015). Depending on the year, some states report more West Nile virus disease cases than others. Some areas of the United States also report other mosquito-borne viruses such as eastern equine encephalitis virus or La Crosse encephalitis virus.

Though anyone can get infected with West Nile virus, some people are at higher risk for neurologic disease. For example, people over the age of 50 are at higher risk for encephalitis (inflammation of the brain).

What are the symptoms of a West Nile virus infection?

No symptoms in most people

Most people (70-80%) who become infected with West Nile virus do not develop any symptoms.

Fever in some people

Figure 2. West Nile virus neurologic disease incidence reported to ArboNET by state in the United States, 2015. View Map.

About 1 in 5 people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Severe symptoms in a few people

Less than 1% of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the lining of the brain and spinal cord). The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis. See your healthcare provider if you think you have symptoms of West Nile virus.


Why risk a severe illness this summer? Take steps to avoid West Nile virus infection.

How do I protect myself from mosquito bites?

  1. Use insect repellent: When used as directed, insect repellent is the BEST way to protect yourself from mosquito bites.  Environmental Protection Agency (EPA)-registered insect repellents are safe for even children and pregnant women. All the EPA-registered insect repellents are evaluated for safety and effectiveness.
    • DEET: Products containing DEET include Cutter, OFF!, Skintastic.
    • Picaridin (also known as KBR 3023, Bayrepel, and icaridin): Products containing picaridin include Cutter Advanced, Skin So Soft Bug Guard Plus, and Autan outside the United States).
    • Oil of lemon eucalyptus (OLE) or PMD: Products containing OLE include Repel .
    • IR3535: Products containing IR3535 include Skin So Soft Bug Guard Plus Expedition and SkinSmart.
  1. Treat clothing and gear: Treat items such as boots, pants, socks, and tents with permethrin or purchase permethrin-treated clothing and gear.
    • Treated clothing remains protective after multiple washings. See product information to find out how long the protection will last.
    • If treating items yourself, follow the product instructions carefully.
    • Do not use permethrin products directly on skin.
  1. Mosquito-proof your home: Take steps to avoid having mosquitoes enter your home.
    • Use screens on windows and doors. Repair holes in screens to keep mosquitoes outside.
    • Use air conditioning when available.
    • Keep mosquitoes from laying eggs in and near standing water around your home.
      • Once a week, empty, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers both inside and outside your home.