City Agencies Step Up Efforts to Stop Spread of West Nile Virus, New Curbside Catch Basin Program Stops Mosquito Breeding at 20,000 San Francisco Locations

(September 15, 2006)

State Reports One Bird Tests Positive for West Nile Virus in San Francisco

San Francisco, CA – Walk past any of the city's 20,000 catch basins and you'll see what looks like a scene from a paintball game: bright spots of colorful markings decorating the concrete shoulders above each catch basin. The array of colors is a visual indication that the catch basin has been treated with a mosquito larvicide to prevent the spread of West Nile Virus.

Earlier this week, San Francisco received notice from the California Vector-Borne Disease Section of the California Department of Health Services that a wild bird found in the Presidio has tested positive for West Nile Virus (WNV). This is the City's first case of WNV in a bird this season. Last year, only two birds tested positive. No human cases have been reported.

The catch basin treatment program is part of the third annual "Fight the Bite" campaign sponsored by the San Francisco Public Utilities Commission (SFPUC), Department of the Environment, Department of Recreation and Parks, Public Works and the San Francisco Department of Public Health all City agencies that work together to prevent the spread of West Nile Virus throughout the City. "Fight the Bite" educates the public about causes, symptoms and ways to prevent West Nile Virus illness by avoiding mosquito bites. Information can be found at

The new mosquito abatement project began last year and is one of the SFPUC's proactive programs to eliminate mosquito breeding in all sources of standing water, such as curbside drains and catch basins. Larvicide will be applied every 21 days to San Francisco's 20,000+ catch basins through October. Catch basins are the biggest single source of mosquito breeding areas in an urban environment.

"As the City's chief water steward, we're taking responsible steps to eradicate mosquito breeding grounds and protect San Franciscans from the spread of West Nile Virus," said SFPUC General Manager Susan Leal. "Educating people about the causes and symptoms of West Nile Virus is just the first step. Just as important are coordinated prevention efforts like our curbside catch basin program."

The detection of antibodies for WNV serves as a reminder that individuals should take basic precautions to protect their health.

"The Presidio has been carefully monitoring for mosquitoes," observed Tia Lombardi, Director of Public Affairs with the Presidio Trust, "and we are treating with biological insecticides as needed."

Throughout the City, technicians from licensed pest control company Pestec travel on bicycle or truck and, after depositing a larvicide in the wet catch basins, mark the basin with a water-soluble color spot. The main chemical used in the catch basin's larvicide application is Methoprene, an insect growth regulator that stunts mosquito development and prevents reproduction. The compound rapidly degrades in water and is non-toxic to humans. Any larvicide residue remaining in the catch basins is flushed down the sewer system to one the SFPUC's wastewater treatment plants for removal.

Significant mosquito problems can be reported to the San Francisco Department of Public Health at (415) 252-3806. Report dead birds to the California Department of Health Services at (877) WNV-BIRD.

For a photo of a Pestec technician treating a catch basin, please contact Tony Winnicker, 415/934-5733.


Department of the Environment

City and County of San Francisco

11 Grove Street, San Francisco, CA 94102

Telephone: (415) 355-3700 • Fax: (415) 554-6393

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