Bird flu has been detected in beef for the first time, the U.S. Department of Agriculture announced Friday, but officials said the meat from a single sickened dairy cow was not allowed to enter the nation's food supply and beef remains safe to eat.

The USDA said the H5N1 virus was found as part of testing of 96 dairy cows that were diverted from the supply because federal inspectors noticed signs of illness during routine inspections of carcasses at meat processing plants. Bird flu was found in only one of those cows.

Bird flu has been confirmed in dairy cattle herds in nine states, has been found in milk and has prompted the slaughter of millions of chickens and turkeys. But finding it in beef is a new development for the outbreak, which began in 2022.

The agency said last month that it would test ground beef for bird flu at retail stores, but it has yet to find any sign of the virus.

Even if bird flu were to end up in consumer beef, the USDA says, cooking the meat to an internal temperature of 165 degrees Fahrenheit will kill it just like it kills E. coli and other viruses.

Two farmworkers at dairies in Michigan and Texas were sickened by bird flu this spring. The danger to the public remains low, but farmworkers exposed to infected animals are at higher risk, health officials said.

Only one other human case of bird flu has been confirmed in the U.S. In 2022, a prisoner in a work program picked it up while killing infected birds at a poultry farm in Montrose County, Colorado. His only symptom was fatigue, and he recovered.

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• Bird Flu