LOS ANGELES — Experts believe three more cats in Los Angeles County have been infected with H5N1 bird flu. Two others succumbed to the disease earlier this month after drinking recalled raw milk from Fresno-based Raw Farm LLC dairies.

Of the three new sick cats, two died and one tested positive for influenza A, an unusual finding in domestic cats that haven’t been exposed to infected birds or contaminated dairy products. The two that died couldn’t be tested while they were alive, but experts believe it is likely their deaths were due to the H5N1 virus.

The three cats all lived in the same household.

Influenza A viruses include most seasonal human flu viruses, as well as H5N1. Health officials are not yet sure where the cats acquired H5N1 — although they noted in a statement they are investigating raw meat as a source and were awaiting test results.

“The risk of H5 bird flu remains low in Los Angeles County, but these confirmed cases of the virus in pet cats are a reminder that consuming raw dairy and meat products can lead to severe illness in cats,” said Barbara Ferrer, director of the Los Angeles County Department of Public Health, in a statement.

She urged county residents “to avoid raw dairy and undercooked meat products, limit contact with sick or dead animals, report sick or dead birds and keep pets or poultry away from wild animals and birds.”

The three latest cats all exhibited respiratory illness, and have no known exposure to raw milk; investigators are looking into whether the animals ate raw meat.

The cats lived exclusively indoors, according to health officials.

People who had direct contact with the cats are being monitored for symptoms and have been offered antiviral medications. There have been cases of cat-to-human transmission of bird flu, according to researchers.

It is unclear how many cats have died since H5N1 began circulating in dairy cows earlier this year. They are extremely susceptible to the virus, however, and dead barn cats are considered an early biological warning that a dairy has been affected by the virus.

At one Texas dairy farm this spring, 12 barn cats died after drinking infected raw milk. Sykes also noted a 2023 outbreak in South Korea, in which shelter cats ate pet food made with H5N1-infected raw duck. In one shelter, 38 of 40 cats died after eating the contaminated food.

Last year, the World Health Organization reported sporadic deaths of cats throughout areas where H5N1 bird flu was circulating, including at one location in Poland, where a cluster of 46 died; 29 of those animals were found to be positive for the bird flu virus.

Larger cats, including captive lions, tigers and panthers, have also died as a result of eating meat contaminated with bird flu. So, too, have wild California bobcats and mountain lions.

Symptoms of H5N1 infection in cats include labored breathing, bloody diarrhea and neurological abnormalities — loss of motor control, seizures, depressed mental state, stiff body movements, blindness, circling, copious eye and nose discharge and coma — with rapid deterioration and death in some cases.

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