West Nile Virus
West Nile virus (WNV) is a disease caused by a virus that is spread through mosquito bites. WNV is found on every continent except Antarctica. It was first detected in North America in 1999, and has since spread across the continental United States and Canada and is well established. Maricopa County had its first WNV outbreak in 2004. See current case counts.
WNV is spread primarily through mosquito bites. WNV is spread to people primarily through the bite of infected Culex species mosquitoes. Culex mosquitoes are found in Maricopa County and other parts of Arizona and we do have mosquitoes infected with WNV. These mosquitoes generally bite from evening to early morning so it is important to protect against mosquito bites whenever you are outside.
WNV can be spread in other ways, too. In rare cases, WNV also can be transmitted during blood transfusions, organ transplants, or from a mother to her baby during pregnancy, delivery, or breastfeeding.
It takes 2-6 days for a person to develop symptoms after being bitten by a mosquito infected with WNV.
Illness with fever in some people. Only 1 out of 5 people with WNV will have symptoms. Individuals may develop a fever with other symptoms, such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people who experience these symptoms will recover completely, although fatigue and weakness can last for weeks or months.
Severe illness in a few people. Severe illness can occur in people at any age; however, people over 60 years of age are at the greatest risk for severe illness. Additionally, individuals with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants are also at greater risk for serious illness. In more severe cases, the illness can affect the brain causing encephalitis (swelling of the brain) or meningitis (swelling of the surrounding brain tissues). The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis. Recovery from severe illness may take several weeks or months and some of the neurologic problems may be permanent. Rarely, death can occur.
Individuals should see a healthcare provider if they develop the symptoms described above. The provider may order blood tests to look for WNV or other similar viruses like SLEV.
There are no specific treatment options. There is no specific medicine or vaccine available for WNV infection. A doctor may recommend rest, fluids, and use of over-the-counter pain relievers to reduce fever and relieve some symptoms.
Fight the Bite, Day and Night!
- Empty, drain or cover sources of standing water around your home to prevent mosquito breeding.
- When possible, wear long-sleeves, long pants, and socks when outdoors. When you go outdoors, use an EPA-registered insect repellent containing DEET.
- Insect repellents containing DEET are safe and effective during pregnancy.
- When using sunscreen, apply sunscreen first and then apply mosquito repellent.
- Do not apply repellent onto hands, eyes, mouth, and cuts or irritated skin.
- Dress your child in clothing that covers arms and legs.
- For children older than 2 months, use insect repellent on exposed skin. Adults should spray insect repellent on their hands and then apply to a child’s face.
- Cover crib, stroller, and baby carriers with mosquito netting.
- Products containing oil of lemon eucalyptus or para-menthane-diol should not be used on children younger than 3 years old.
Office of Epidemiology & Data Services
4041 N Central Avenue
Phoenix, AZ 85012
Phone : 602-506-6767Fax : 602-372-8935