Health officials said Monday that H5N1 bird flu was discovered last month in two asymptomatic chickens at a live bird market in San Francisco, but there are no signs the public has been exposed.
The bird flu virus was found as part of routine testing at live bird markets in the state by the California Department of Food and Agriculture.
Market workers who had close contact with the birds were monitored and reported no symptoms after a 10-day period, said San Francisco Director of Public Health Dr. Grant Colfax in a report that will appear on the health committee agenda on Tuesday.
No members of the public were exposed and the market has since reopened.
“At this time, no human cases of H5N1 have been reported and H5N1 remains a low risk to the general public,” the department said in a statement Monday.
After the virus was discovered in chickens, WastewaterSCAN, a national partnership that monitors infectious diseases in municipal wastewater systems, found fragments of H5N1 genetic material in the city’s wastewater. Another test found no fragments and the health department is investigating to learn more about the interpretation of the findings.
“It is possible that the H5N1 fragments found in wastewater come from birds or other animals because of San Francisco’s unique combined sewer system that collects and treats both wastewater and stormwater in the same network of pipes,” the health department report said .
San Francisco is the only city in California with a positive H5N1 detection so far.
The Centers for Disease Control is closely monitoring H5N1 avian flu, including recent outbreaks in dairy cattle and one case to date of spread from cattle to a dairy worker in Texas, reported on April 1, 2024.
The public should avoid touching all wild animals, including sick or dead birds, and continue to take protective measures, such as only consuming milk or dairy products that have been pasteurized.
“There is currently no evidence that the H5N1 virus is spreading from person to person, but that is what the CDC is closely monitoring and trying to prevent,” the health department said. “At this time, it appears that the likelihood of bird flu causing an outbreak in humans remains low.”
