CDC Features - West Nile Virus and Preventing Mosquito Bites

CDC Features - West Nile Virus and Preventing Mosquito Bites

West Nile Virus and Preventing Mosquito Bites

Stay healthy this summer. Protect yourself and your loved ones from mosquito bites that cause West Nile virus infection.

2012 was the largest and most deadly outbreak of West Nile virus (WNV) since 1999 when it first appeared in New York. The best way to prevent West Nile virus disease is to avoid mosquito bites.
It only takes a single mosquito bite to make you or your family member sick with West Nile virus - just one bite could make you or your loved one sick, cause severe illness, or even death.  Don’t risk your health this summer!

Know the facts

More than 37,000 people in the U.S. have been reported with West Nile virus disease since 1999, and of those over 16,000 have been seriously ill and more than 1,500 have died. Many more cases of illness are not reported to CDC. It is estimated that over three million people from every state (except Alaska and Hawaii) have been infected (780,000 became sick) in the 14 years since West Nile virus came to the U.S.

Know your risk

All 48 states in the continental U.S. have had human West Nile virus cases. Though anyone can get infected with West Nile virus, there are people at higher risk for severe disease. People over the age of 50 are at higher risk for encephalitis. The reasons one person becomes severely ill and another doesn't aren't entirely known.
West Nile virus (WNV) neuroinvasive disease incidence reported to ArboNET, by state, United States, 2012

View map of infections occurring in 2012  [PDF - 170KB].
See also detailed case counts by state  [PDF - 270KB].

Where is West Nile virus a problem?

Some states, such as those in highlighted in black on the map to the right, had greater concentrations of cases of severe disease than others represented in lighter colors in 2012. This can change each year. Some areas of the U.S. are affected by other viruses such as eastern equine encephalitis virus, LaCrosse encephalitis virus, and dengue.

Insect repellent: What you need to know

Why take a chance? Prevention is up to you. No one is safe from West Nile virus, but there are steps you can take to help prevent an infection. Avoid the weeks (to months) of aches and fatigue that come with West Nile fever, or the more severe problems of being hospitalized with encephalitis or meningitis (inflammation of the brain and surrounding tissues).

1. Apply insect repellent on exposed skin and clothing when you go outdoors. Use an Environmental Protection Agency (EPA)-registered insect repellent. Permethrin sprayed on clothing provides protection through several washes. Don’t spray repellent on skin under clothing and don’t use permethrin on skin.
2. Cover up! Wear long sleeve shirts and long pants and socks while outdoors to prevent mosquito bites.
3. Avoid mosquitoes. The mosquitoes that spread West Nile virus bite between dusk and dawn. Limit the amount of time you spend outdoors during these hours. If you are outside, be sure to wear repellent and protective clothing.
4. Support your local community mosquito control programs. Mosquito control activities are most often handled at the local level, such as through county or city government. The type of mosquito control methods used by a program depends on the time of year, the type of mosquitoes to be controlled, and the habitats where the mosquitoes live. Methods can include eliminating mosquito larval habitats, applying insecticides to kill mosquito larvae, or spraying insecticides from trucks or aircraft to kill adult mosquitoes. Your local mosquito control program can provide information about the type of products being used in your area. Check with your local health department for more information.

What repellent should I use?

CDC recommends a variety of effective repellents. The most important step is to pick one and use it. There are those that can protect you for a short while in the backyard or a long while in the woods. DEET, picaridin, IR3535 and the plant-based oil of lemon eucalyptus are all repellents recommended by CDC. All contain an EPA-registered active ingredient and have been evaluated for efficacy and safety. EPA has a long listing of every registered repellent brand in the U.S. There are good repellents for every budget, age and preference.

Know the symptoms of West Nile 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.
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 brain or surrounding tissues). The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis. See your healthcare professional if you think you have the symptoms of West Nile infection.
Resources for additional West Nile virus information
For more WNV information, see CDC’s West Nile virus site or EPA’s registered repellent information.
The American Academy of Microbiology (AAM) published a comprehensive report in 2013 called West Nile virus FAQ  [PDF - 1.6MB].