Los Angeles County health officials say they have found the H5N1 bird flu virus in wastewater collected at the AK Warren Water Resource Facility in Carson.
The “hit” of the virus was discovered on Oct. 28 is WastewaterSCAN, an infectious disease monitoring network run by researchers at Stanford, Emory University and Verily, an Alphabet Inc. corporation.
Hits were also seen last week in San José, Redwood City, San Francisco, Palo Alto, Sacramento, Santa Cruz, Marina and Turlock.
The Carson plant harvests wastewater from about 50% of LA County's population, Annabelle de St. Maurice, director of the LA County Department of Public Health's Department of Public Outbreak and Disease Surveillance.
Officials say they have not identified the source of the virus, but suggested several possibilities, including contaminated animal waste and contaminated wild bird droppings. They are also “fully engaged with key risk groups,” including nearby dairy and meat farms.
“The most likely sources seem to come from animal products, rather than wild birds,” said De St. Maurice.
He said the risk to the public remains low.
H5N1 bird flu has been found in 203 California dairy herds since August; There are 17 dairy workers infected with the virus. Nationwide, 41 people have been infected with the virus – 21 from dairy cows, 19 from chicken and one unknown. USDA reported 404 positive dairy herds in 14 states. This number does not include the eight herds found earlier this week in Utah.
It was also completely recovered from a pig from Oregon.
De St. Maurice said the county regularly monitors and checks for birds, domestic animals and wild mammals.
In addition, he said, the district is working within the community to obtain samples of mild influenza collected from health clinics and hospital samples “to see if there are any human cases of H5N1.”
He mentioned that the public health department of this region is also doing “communication and education in vulnerable communities,” but he said, so far, there have been no human cases.
De St. Maurice said it was this type of work — subtyping flu samples — that enabled Missouri health officials to identify a human case of H5N1 that had not been reported to have come into contact with milk or poultry. The source of that person's infection is still unknown.
The discovery of the contaminated water comes as the virus spreads to California dairy cattle — which now accounts for more than half of the reported cattle diseases in the country — and as wild bird migration from the Arctic moves south along the Pacific Flyway.
There are now two strains of H5N1 bird flu circulating in California. The form that surrounds dairy cows is known to scientists as B3.13. A new version of the wild bird, which appeared recently, is known as D1.1 or D1.2.
Genetic sequencing of the H5 virus found in Los Angeles County wastewater was not performed. According to De St. Maurice, the way the samples are taken and identified does not allow sequencing.
H5 viruses are from birds; they are not human viruses.
In a statement, officials said people can reduce the chance of infection by avoiding raw milk, raw cheese and undercooked meat. Pasteurization and adequate cooking inactivates the virus.
They also recommend that people avoid unprotected contact with sick or dead animals, and avoid items contaminated with bird droppings. Pets can also be infected by these methods. And officials ask that people report sick or dead birds to local animal control agencies.
They also recommend that people get an annual flu shot. While the seasonal flu vaccine won't prevent bird flu infection, it does reduce the chance that bird flu will mix with human flu – potentially creating a new virus that can easily spread between people.
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