Bird flu detected in San Diego County wastewater

SAN DIEGO (FOX 5/KUSI) — San Diego County is now the fifth location in California to detect the bird flu, county officials announced Monday.

San Diego County reports though there are no confirmed human cases, the H5 influenza virus — commonly known as the bird flu — was detected in wastewater in San Diego County during testing on Sept. 1, 2024.

After follow up sampling, county health officials say the virus was only detected that once, and they are investigating how the virus got into the wastewater system as there have been no reported human cases in the county.

H5 influenza circulates in wild birds and can be spread to humans, though it is more rare.

According to the county, San Diego’s sewage system is closed, which means the stormwater and wastewater systems are not mixed, prompting officials to determine the cause of the virus in the wastewater was most likely from environmental sources.

The county says there have been no detections of bird flu in cattle, birds or humans in San Diego County in 2024. However, there were some detected in wild birds in 2022 and 2023, and a poultry flock was infected in 2022.

According to the CDC, there have only been 15 human cases of the bird flu across the U.S. since 2022. To date, there have been no reported cases of H5N1 bird flu in humans in California.

“San Diego County has a robust flu surveillance system,” said Dr. Ankita Kadakia, County interim public health officer. “While we have no evidence of the virus in people or animals, it is important to be transparent with the public both about the detection status and that we are vigilant and working with our partners at the California Department of Public Health, California Department of Food and Agriculture, and California Department of Fish and Wildlife to monitor for signs of H5 presence locally.”

The San Diego County Health and Human Service Agency reports current outbreaks of H5N1 in poultry in the U.S. were first detected in 2022, and in diary cows in 2024.

The best way to prevent getting sick from the bird flu is to avoid interacting with wild or domestic birds, as well as other animals with suspected or confirmed cases.

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