What is West Nile Virus? 

West Nile virus is a virus carried by mosquitoes.You can get West Nile virus if an infected mosquito bites you. Some people who get West Nile virus have mild symptoms, but others have a serious illness. People over age 50 and with certain medical conditions are more likely to become very sick or die if they get infected by West Nile virus.

Most people are bitten doing everyday activities around their own home like gardening, sitting outside, and picnicking. Some are infected while traveling to places where mosquitoes and West Nile Virus are more common.  The best way to prevent getting West Nile virus is to keep mosquitoes from biting you by wearing insect repellent and by wearing long pants and long sleeved shirts.

Symptoms of West Nile Virus

Symptoms of West Nile virus usually will appear 3 to 14 days after being bitten by an infected mosquito.

Most people with West Nile virus will not have any symptoms. However, older people or the immune-compromised, such as those on cancer chemotherapy, are more likely to get West Nile virus.

Common symptoms of West Nile virus include fever, headache, body aches, and sometimes skin rashes or swollen lymph nodes. These symptoms may last a few days, but there are reports of prolonged fatigue and muscle weakness.

Serious symptoms include headache, high fever, neck stiffness, disorientation, coma, tremors, muscle weakness, loss of vision, convulsions, numbness, and paralysis. These symptoms may last several weeks and can cause permanent
nervous system damage. 

Seek medical attention right away if you have any of these symptoms.

West Nile virus infection can sometimes be fatal. There is no specific treatment for West Nile virus infection and there is no human vaccine.

While the risk of getting West Nile virus from a mosquito bite is small, it is easy to protect yourself from infection.

West Nile Virus Surveillance Data

Please click to view the Communicable Disease dashboard with local West Nile virus data available in English and Spanish.

United States data is available at the Centers for Disease Control and Prevention's website.

For More Information 

• California Department of Public Health (CDPH) West Nile virus website
• California Department of Public Health (CDPH) - West Nile Virus What You Need to Know in English and Spanish
• Monterey County Mosquito Abatement District

Information for Medical Providers

• CDC West Nile Virus Diagnosis Flowchart
• CDC Clinical Testing and Diagnosis of West Nile Virus
• CDC West Nile Virus Clinical Training - Free CME Credit