Last month, two chickens at a live bird market in San Francisco tested positive for H5N1 avian flu, authorities announced on Monday.
The San Francisco Department of Public Health reported that state health officials discovered the infected, asymptomatic birds during routine monitoring by the California Department of Food and Agriculture. This testing is part of the current national bird flu outbreak response. told by The Star
“There is no threat to public health at this time,” stated Dr. George Han, Director of Communicable Disease Prevention & Control at the San Francisco Department of Public Health. “There have been no human cases.”
Health officials closely monitored market employees who had contact with the chickens. Over 10 days, none reported symptoms. No public exposure occurred, and the market in the city’s Bayview neighborhood has since reopened safely.
“In situations like this, we work diligently in the background to ensure we are prepared if there is a potential threat to human health,” Han added.
Following the detection at the bird market, WastewaterSCAN, a national initiative monitoring infectious diseases through municipal wastewater, began testing San Francisco’s wastewater for the H5 marker. Initial tests detected fragments of H5 genetic material, making San Francisco the only municipality in California with a positive avian flu detection. However, follow-up tests later in May showed no H5 fragments.
According to NBC News, The agency is investigating the origins of these genetic traces, considering the city’s unique combined sewer system, which treats both wastewater and stormwater.
“It’s unique. We take in everything that goes into the storm drains, including any animal waste from birds or other animals,” Han explained.
An increase in flu viruses detected at wastewater treatment plants in California recently has raised concerns that the H5N1 bird flu may be spreading more rapidly than anticipated, potentially putting the state’s 1.7 million dairy cows at risk for infection.
Health officials have observed multiple spikes in influenza A viruses, which include the H5N1 avian flu strain that has killed millions of birds worldwide and infected dozens of dairy cow herds across nine U.S. states.
“We are definitely taking this seriously. This is the first time we are seeing avian flu in cows. We hadn’t seen that previously,” Dr. Mandy Cohen, Director of the Centers for Disease Control and Prevention, told the Associated Press. “The fact that it is in cattle now definitely raises our concern level.”
According to data from approximately 700 sites published by the CDC, the Bay Area is a hotspot for flu activity, with nearly all monitored facilities in the region showing moderate to high increases in influenza A viruses. However, San Francisco hospitals have not observed an increase in undiagnosed upper respiratory illnesses. told by Reuters
“Our levels, as far as we can tell, have not increased significantly in recent weeks,” Han said.
Though the avian flu poses minimal risk to humans, its spread among livestock could disrupt food supplies and potentially lead to a pandemic if it mutates to enable human-to-human transmission.
As of now, no cases of infected herds have been reported in California, the leading milk-producing state in the U.S., with around 1,300 dairy farms.
The current strain of avian flu emerged among birds in 2022 and was first detected in dairy cows in the U.S. in late March, marking the first known instance of bird flu viruses in cows.
“It’s not a new strain of the virus,” Cohen said. “So this is known to us. We’ve been studying it. And, frankly, we’ve been preparing for avian flu for 20 years.”
Since then, it has spread to 49 herds of dairy cattle across nine states: Texas, Michigan, Kansas, Colorado, Idaho, New Mexico, North Carolina, South Dakota, and Ohio, according to the Department of Agriculture.
There have been only four reported cases of avian flu infection in people in the U.S. One case occurred in Colorado in 2022, involving an individual who worked closely with infected poultry. The other three cases were more recent — one in Texas in March and two in Michigan last month — involving people employed at dairy farms.
The current strain of bird flu has developed numerous mutations, according to a new study, which may increase its ability to spread between species and reduce its susceptibility to antiviral drugs.
“This is a new development,” Cohen said. “Cows and other mammals being a reservoir gives this virus a new opportunity to change. That’s what we’re watching for really closely.”
Han assured that there is no cause for concern in San Francisco for now.
“The reason we’re discussing this is to be transparent about the daily work public health officials do,” he said. “Experts are monitoring and analyzing these developments to ensure we are ready to act if anything changes.”
FAQs on Avian Influenza
Can people get sick from H5N1? Yes, though rare, people can get infected through direct contact with infected birds or contaminated environments.
What are the symptoms of H5N1 in humans? Symptoms include fever, cough, sore throat, muscle aches, and in severe cases, respiratory difficulties and pneumonia. “So far, human cases have been very mild,” Han said.
How does H5N1 spread? H5N1 spreads primarily through direct contact with infected birds, their droppings, or contaminated surfaces. It does not usually spread from person to person.
How can I protect myself from H5N1? Avoid direct contact with wild birds and poultry that appear ill. Practice good hygiene, including regular hand washing and using alcohol-based hand sanitizers.
“Continue everyday common sense practices, like drinking pasteurized milk, preparing meat properly, and avoiding wild animals,” Han advised.
Is there a vaccine available for H5N1? Vaccines are primarily used for high-risk groups such as poultry workers and are not generally available to the public.
Should I avoid public parks with bird populations? No, but avoid touching wild birds and their droppings, and wash your hands thoroughly if you come into contact with potentially contaminated surfaces.
What should I do if I find a dead bird? Do not touch it. Report it to local animal health authorities who can safely remove and test the bird for avian influenza.
Can I still eat chicken or duck? Yes, ensure poultry is cooked to an internal temperature of at least 165°F (74°C), which kills the virus.
Is it safe to keep pet birds? Yes, but practice good hygiene, regularly clean cages, and monitor the health of your birds closely.
Do I need to wash my hands after filling a bird feeder? Yes, it is recommended to wash your hands after filling a bird feeder to reduce any risk of infection from wild bird droppings or contaminated surfaces.
