Press Release

August 15, 2005
Eileen Shields, Public Information Officer, 415/554-2507

San Francisco Announces First Human Case of West Nile Virus

Patient Home and Recovering

San Francisco, CA—A middle-aged San Franciscan with neurological symptoms has been diagnosed with West Nile Virus (WNV) disease. This is the City’s first reported case of the mosquito-borne illness. The patient is recovering at home.

Further investigation will be conducted to help evaluate whether the disease was acquired in San Francisco or elsewhere. Over 35 San Francisco birds have been tested for the virus this year and none have been found positive. Typically, WNV cases in birds precede human cases.

“The appearance of West Nile Virus in San Francisco is not a surprise,” said Rajiv Bhatia, MD, MPH, Director of Environmental Health. “As the virus has moved westward across the United States, we have been preparing for its arrival.”

So far in 2005 have been 175 human cases of the West Nile virus reported in California, with most of the cases in Sacramento and Riverside Counties. There have been 4 fatalities. In the United States, almost 10,000 human cases of WNV have been reported since it was first detected in the United States in New York in 1999.

Most individuals who become infected with WNV will not experience any illness. Others will have only mild symptoms, such as fever, fatigue, nausea, headache, muscle aches, skin rash, or swollen lymph nodes. However, WNV can affect the elderly and individuals with compromised immune systems with more severe illness.

WNV is transmitted to humans and animals through a mosquito bite. Mosquitoes become infected when they feed on infected birds. Human-to-human transmission of WNV generally does not occur.

San Francisco is taking several steps to limit risks to residents. The City’s mosquito control program includes: collecting birds for testing, monitoring ponds and other possible mosquito breeding sites, trapping to detect high numbers of mosquitoes, treating sewer catch basins to prevent breeding, and educating residents and owners about removing standing water from private property and avoiding mosquito bites.

Individuals can reduce their risk of mosquito-borne diseases by taking these precautions:

• Avoid spending time outside when mosquitoes are most active, especially at dawn and dusk.
• When outdoors, wear long pants and long-sleeved shirts.
• Apply insect repellent according to label instructions.
• Make sure that doors and windows have tight fitting screens. Repair or replace screens that have tears or holes.
• Eliminate all sources of standing water on your property that can support mosquito breeding.
• Contact the Department of Public Health, Mosquito Control program at 415-252-3806 if there is a significant mosquito problem where you live or work.

More information about West Nile Virus and San Francisco’s prevention activities can be found at the websites, http://www.sfmosquito.org, http://www.sfdph.org/ehs/WestNile.htm and www.westnile.ca.gov.