As federal and state health officials expand their avian flu surveillance, the San Francisco Department of Public Health has reported that avian flu has been detected in wastewater samples collected in May.
The samples were collected after two chickens at a live bird market in the city tested positive for the disease on May 9.
Authorities say the source of H5N1 in San Francisco’s wastewater is unclear and that the city’s sewer system incorporates both wastewater and stormwater — meaning it could be coming from animal waste, milk or people, or from a combination of sources.
City officials said the virus has not been detected in more recent wastewater analyses, which have been analyzed by WastewaterSCAN — an infectious disease monitoring network run by researchers at labs at Stanford, Emory University and Verily, Alphabet Inc.’s life sciences research organization.