Bird flu virus found in Los Angeles County wastewater

Los Angeles County health officials said they discovered the H5N1 bird flu virus in wastewater at the AK Warren Water Resource Facility in Carson.

The viral “hit” was discovered Oct. 28 by WastewaterSCAN, an infectious disease surveillance network run by researchers at Stanford University, Emory University and Verily, Alphabet Inc.'s life sciences arm.

Last week also saw hits in San Jose, Redwood City, San Francisco, Palo Alto, Sacramento, Santa Cruz, Marina and Turlock.

The Carson plant processes wastewater from about 50% of L.A. County's population, said Annabelle de St. Maurice, director of community outbreak and syndromic surveillance for the L.A. County Department of Public Health.

Officials say they have not identified the source of the virus but suggested a few possibilities, including discarded contaminated animal products and infected wild bird feces. They are also “actively engaging with key risk groups,” including nearby dairies and meat processing plants.

“The likely sources appear to be animal products rather than wild birds,” De St. Maurice said.

She said the risk to the public remains low.

H5N1 avian influenza has been detected in 203 California dairy herds since August; 17 dairy workers were also infected. Across the country, 41 people have been infected – 21 from dairy cows, 19 from poultry and one unknown. The USDA has reported 404 positive dairy herds in 14 states. That number does not include eight herds discovered in Utah earlier this week.

It has also been conclusively demonstrated in a pig from Oregon.

De St. Maurice said the county routinely monitors and tests birds, pets and wild mammals with symptoms.

In addition, she said, the county is working within the community to subtype flu samples collected at health clinics and hospitals “to see if there are any potential H5N1 cases in humans.”

She noted that the county health department is also conducting “outreach and education efforts for at-risk communities,” but said there have been no human cases so far.

De St. Maurice said it was this type of work – subtyping flu samples – that allowed Missouri health officials to identify a human case of H5N1 in which no contact with dairy or poultry was reported. The source of this person's infection is not yet clear.

The wastewater findings come as the virus is spreading among California dairy cows — which now account for more than half of the country's reported cattle infections — and as the fall migration of wild birds from the Arctic moves south along the Pacific Flyway.

There are now two strains of H5N1 bird flu circulating in California. The form circulating in dairy cows is known by scientists as B3.13. A new wild bird version that has recently emerged is known as D1.1 or D1.2.

Genetic sequencing of the H5 virus found in Los Angeles County wastewater has not been performed. According to De St. Maurice, the way the samples are collected and identified does not allow for sequencing.

H5 viruses come from birds; These are not human viruses.

In a statement, officials said people can reduce their risk of infection by avoiding raw milk, raw cheese and undercooked meat. The virus is inactivated through pasteurization and sufficient cooking.

They also recommend avoiding unprotected contact with sick or dead animals and avoiding materials contaminated with bird droppings. Pets can also become infected this way. And officials are urging people to report sick or dead birds to local wildlife authorities.

They also recommend getting a flu shot annually. Although the seasonal flu vaccine does not prevent bird flu infection, it does reduce the chance of bird flu combining with human flu – potentially creating a new virus that could spread more easily among people.