The Food and Drug Administration is investigating the spread of "a highly contagious and often deadly" bird flu to dairy cows in Texas, Kansas and Michigan, the agency said on Friday.

The big picture: The bird flu was detected in unpasteurized milk samples and swabs from two dairy herds in Texas and Kansas and one in Michigan, but federal authorities said in an online Q&A there is "no concern" about the safety of the U.S. milk supply.

• Testing for the "highly pathogenic avian influenza," more commonly referred to as the bird flu, is also happening in cow herds in New Mexico and Idaho and two added herds in Texas.
• Symptoms include decreased lactation and low appetite.

Threat level: Federal authorities said there is no concern of a related consumer health risk. "Pasteurization is required for any milk entering interstate commerce," the FDA said.

• The agency also said milk loss from sick cows is "too limited to have a major impact on supply." That means "there should be no impact on the price of milk or other dairy products," the FDA said.

Yes, but: The FDA has limited research on whether the flu can be transmitted through raw, unpasteurized milk or other dairy products that use raw milk, like cheese.

• The agency recommends against buying and selling such products when cows show signs of illness even if the cheese will undergo the required 60-day aging process.

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