West Nile Virus Information & Links

What Is It?  West Nile virus is a disease-causing virus spread by mosquitoes.  West Nile virus first appeared in the U.S. in 1999 and is transmitted to humans through the bite of an infected mosquito.  It cannot be spread person to person.

Where Is It? In 2003, three locally acquired human WNV cases were detected in residents of Los Angeles, Imperial, and Riverside counties, and WNV activity was detected in dead birds, mosquitoes, sentinel chickens, and a horse in six southern California counties. West Nile virus has also been detected in 2004 in southern California.  The California Department of Health Services has confirmed that mosquitoes collected from south Sacramento County have now tested positive for West Nile virus. 

Where Has West Nile Virus Been Reported?:  U.S. Maps and Surveillance Information

Current Case Count

Mosquito surveillance and control efforts are being stepped up throughout the state, and residents are asked to take precautions during evening and early morning hours when mosquitoes are most prevalent.

What Can You Do?

You can take the following personal safety precautions recommended by the California Department of Health Services:

• Avoid spending time outside when mosquitoes are most active, at dawn and dusk, and especially for the first two hours after sunset.
• When outdoors, wear long pants, long-sleeved shirts and other protective clothing.
• Apply insect repellent containing the active ingredient DEET when outdoors, according to label instructions.
• Exclude mosquitoes from your home with tight fitting screens on doors and windows.
• Eliminate all sources of standing water on your property that can support mosquito breeding.
• Report significant mosquito infestations to your local Vector Control District

Report Dead Birds.  The public is also encouraged to assist in the efforts to detect and monitor WNV by calling the WNV hotline if they find a crow, raven, magpie, jay, sparrow, finch, or hawk that has been dead for about a day. Birds play an important role in maintaining and spreading this virus. Mosquitoes acquire the virus from infected birds, and then transmit the virus to people. Evidence of the virus in dead birds is often the first indication that WNV has been introduced into a new region. DHS has set up a toll free hotline for the public to report dead birds: 877-WNV-BIRD.

What are the Symptoms and Treatment of WNV?

Most people who are bitten by a mosquito with WNV will not get sick. People who do become ill may experience mild to moderate flu-like symptoms like fever, headache and body ache. It is estimated that less than 1% of the people who are infected with WNV become severely ill and require hospitalization. The elderly and immunocompromised are particularly susceptible to illness caused by WNV.

•  Currently there is no specific treatment for WNV infection. Since it is a virus it does not respond to antibiotics. In severe cases hospitalization and supportive care is important.

•  If you have symptoms of West Nile virus, call your doctor.

For further information about West Nile Virus, visit these web sites

California West Nile Virus Surveillance Information Center

California Department of Food & Agriculture West Nile Virus Information

Centers for Disease Control and Prevention Division of Vector-Borne Infectious Diseases National Center for Infectious Diseases

Questions and Answers About West Nile Virus

Publications About West Nile Virus

West Nile Virus in the News

West Nile Virus Protection and Control Act