West Nile Virus
Don’t let mosquitoes wreck your summer. Protect yourself and your family from mosquito bites.
Summertime means mosquitoes and West Nile virus (WNV) season. A bite from an infected mosquito can make you or a family member sick. In the United States, cases are reported from summer and continue into fall. WNV is the most common pathogen spread by mosquitoes in the continental United States.
Stay healthy this summer. Take steps to prevent mosquito bites.
The most effective way to avoid getting WNV is to prevent mosquito bites.
- Use insect repellent: When used as directed, Environmental Protection Agency (EPA)-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women. Use an (EPA)-registered insect repellent with one of the following active ingredients:
- Oil of lemon eucalyptus (OLE)
- Para-menthane-diol (PMD)
- Cover up: Wear long-sleeved shirts and long pants.
- Keep mosquitoes outside: Use air conditioning or window and door screens.
When used as directed, insect repellents are the BEST way to protect yourself and family members from getting sick from mosquito bites.
More than 2,002 cases of people sick from WNV were reported to CDC in 2017. Though the total number of cases differ from year to year and state to state, since WNV was introduced in 1999, all 48 continental United States have reported cases. Some areas of the United States also report cases of other viruses spread by mosquitoes, such as eastern equine encephalitis virus or La Crosse encephalitis virus.
Though anyone can get infected with WNV, some people are at higher risk for severe disease, involving the brain or spinal cord. For example, people over the age of 60 are at higher risk for encephalitis (swelling of the brain).
Symptoms of WNV
No symptoms in most people. Most people (8 out of 10) infected with WNV do not develop any symptoms.
Mild illness with fever in some people. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people recover completely, but feeling tired and weakness can last for weeks or months.
Serious symptoms in a few people. About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).
- Symptoms of severe illness include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis.
- Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.
- Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent.
- About 1 out of 10 people who develop severe illness affecting the central nervous system die.
Control mosquitoes in and around your home
Remove standing water where mosquitoes lay eggs
- Once a week, empty and scrub, turn over, cover, or throw out any items that hold water like tires, buckets, planters, toys, pools, birdbaths, flowerpot saucers, or trash containers. Mosquitoes lay eggs in or near water.
- Tightly cover water storage containers (buckets, cisterns, rain barrels) so that mosquitoes cannot get inside to lay eggs.
- For containers without lids, use wire mesh with holes smaller than an adult mosquito.
- Use larvicides to treat large containers of water that will not be used for drinking and cannot be covered or dumped out.
- If you have a septic tank, repair cracks or gaps. Cover open vent or plumbing pipes. Use wire mesh with holes smaller than an adult mosquito.
Keep mosquitoes out!
- Install or repair and use window and door screens. Do not leave doors propped open.
- Use air conditioning when possible.
- Page last reviewed: August 6, 2018
- Page last updated: August 6, 2018
- Content source:
- National Center for Emerging, Zoonotic, and Infectious Diseases, Division of Vector-Borne Diseases
- Page maintained by: Office of the Associate Director for Communication, Digital Media Branch, Division of Public Affairs