Frequently Asked Questions
What is West Nile Virus?
West Nile Virus (WNV) is a disease spread by mosquitoes, and caused by a virus. WNV first appeared in the United States in 1999, when at least 62 people in the New York City area became ill and seven people died.
How do people get West Nile Virus?
West Nile Virus is transmitted to people by the bite of an infected mosquito. The mosquito gets infected with the virus after feeding on a bird or horse infected with the West Nile Virus. Not all mosquitoes transmit WNV.
There is currently no evidence that WNV is transmitted from person to person.
What animals can get West Nile Virus?
West Nile Virus most often affects birds, but occasionally can cause the disease in other animals, particularly horses. Most horses bitten by mosquitoes will not become ill with WNV. WNV does not usually cause illness in dogs and cats.
There is a vaccine available for horses against West Nile Virus.
There is no evidence of animal to human transmission.
What are the symptoms of West Nile Virus?
Most WNV infections produce no symptoms in people or symptoms are mild to moderate. Symptoms may include: fever, headache, body aches, skin rash, and swollen lymph glands. More severe cases can cause headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. In very rare situations, - WNV can cause death.
More information about the symptoms from Centers for Disease Control
Who is at risk of getting West Nile Virus?
Everyone is at risk of getting WNV, particularly:
How is West Nile Virus treated?
There is no specific treatment for West Nile Virus, but the symptoms can be treated. In severe cases, hospitalization might be required.
There is no vaccine for humans against West Nile Virus.
What can be done to protect against West Nile Virus?
What is the incubation period in humans (i.e., time from infection to onset of disease symptoms) for West Nile disease?
Usually 2 to 15 days.
Where can I get tested for West Nile Virus?
People who have no signs or symptoms of West Nile Virus are not advised to get tested. People with symptoms such as fever, headache, chills, swollen lymph nodes, rash and fatigue should contact their health care provider who will determine whether testing is needed. People who do not have health coverage can contact Contra Costa Health Services at 1-800-771-4270 to make an appointment and enroll in health coverage or visit one of the community clinics in their area.
For more information about mosquito control, call:
Content provided by the Public Health Division of Contra Costa Health Services.