The San Mateo County Mosquito and Vector Control District decided to fog after two crows and mosquitoes were found to be carrying the virus in Menlo Park's 94025 zip code.
Trucks began spraying Zenivex at 9 p.m. on Aug. 11 and wrapped up by 2:30 a.m. the next morning, district officials said. The treated area was roughly bordered by University Drive to the north; Bay Laurel Drive to the east; Altschul Avenue and Sharon Road to the south; and Camino Al Lago to the west.
Dead mosquitoes were then collected from traps and tested. None were positive for West Nile virus, so no further foggings are scheduled for now.
Mosquitoes transmit the virus through biting. Although the primary hosts are birds, West Nile virus also infects people, horses and other animals.
Standing pools of water should be drained to discourage mosquitoes from proliferating, and people should apply repellent while outside and make sure door screens fit tightly, the district advised.
An online petition asking the county to cancel the Aug. 11 fogging gathered 387 signatures and the attention of Menlo Park Mayor Ray Mueller, to no avail.
Mr. Mueller posted that he and county Supervisor Dave Pine had asked that the fogging be delayed for two days if it would not endanger public health to allow time for a public hearing, but the county denied the request.
A public forum will be held to address any concerns about the spraying, although a date and time have not yet been set, according to the district. A representative from Central Life Science, the company that makes Zenivex, will attend.
Go to smcmad.org or call 344-8592 for more information.