Bird flu has hit U.S. dairy cattle for the first time. Here's what it means for milk supply.

Multiple U.S. agencies said on Friday that for the first time, the rampant bird flu has spread to dairy cattle. Impacted cows have been found across several states as officials reemphasize the importance of only consuming pasteurized dairy products. 

The U.S. Department of Agriculture, Food and Drug Administration and Centers for Disease Control and Prevention confirmed the spread of the the bird flu, saying they tested sick cattle from dairy farms in Kansas and Texas. Those tests came back positive for highly pathogenic avian influenza (HPAI), which has been impacting bird populations in Europe and Asia since August 2020 and "caused extensive morbidity and mortality events" in similar species across the U.S., according to the Fish and Wildlife Service. 

This marks the first time the bird flu has been found in dairy cattle, the American Veterinary Medical Association said, and the findings came just days after the virus was detected in goats on a Minnesota farm. In the fall, the bird flu also hit the polar bear species for the first time, killing one of the bears, and it has also spread to marine animals, killing tens of thousands of seals and sea lions.

Bird flu was suspected of impacting U.S. cattle after dairy cows were found to be experiencing "decreased lactation, low appetite and other symptoms," agencies said in a joint news release. On March 25, they said milk samples showed two farms in Kansas and one in Texas were impacted. A swab from another dairy farm in Texas also yielded a positive result, they said. 

Bird flu was later found in a Michigan herd that had recently received cows from Texas, and "presumptive positive test results have also been received for additional herds in New Mexico, Idaho and Texas," officials said. 

Certain animal species that contract the virus usually do so from eating sick or infected birds. Among the dairy cows, however, officials say "transmission between cattle cannot be ruled out" based on reported symptoms and testing results. Those who own dairy cattle have been urged to minimize moving their cattle and test them when they do. They also recommended that sick cows be isolated. 

How will the bird flu impact U.S. milk supply? 

While impacted cattle are experiencing a decline in how much milk they produce, the government said that so far, the milk loss "is too limited to have a major impact on supply." 

"There should be no impact on the price of milk or other dairy products," the agencies said. "Further, the U.S. typically has a more than sufficient milk supply in the spring months due to seasonally higher production." 

There is also no concern from the agencies that milk in the commercial supply is unsafe. All milk products must be pasteurized and only milk from healthy animals is allowed to be sent to processing for human consumption, they added. 

"Milk from impacted animals is being diverted or destroyed so that it does not enter the human food supply," agencies said. "In addition, pasteurization has continually proven to inactivate bacteria and viruses, like influenza, in milk. FDA's longstanding position is that unpasteurized, raw milk can harbor dangerous microorganisms that can pose serious health risks to consumers, and FDA is reminding consumers of the risks associated with raw milk consumption in light of the HPAI detections." 

The spread of bird flu to cattle comes just weeks after Texas cattle ranchers in the panhandle were devasted by the state's largest-ever wildfire. In the wake of the fires, thousands of dead cows had to be picked up across the scorched region. 

"Our producers in the Texas Panhandle have already endured enough," Texas Agriculture Commissioner Sid Miller said, calling the situation "unprecedented." "The Texas Department of Agriculture will use every resource available to maintain the high standards of quality and safety that define Texas agriculture." 

Can bird flu spread to humans? 

While there have been cases of bird flu spreading to humans, health officials have said that these instances remain rare. 

"Initial testing by the National Veterinary Services Laboratories has not found changes to the virus that would make it more transmissible to humans, which would indicate that the current risk to the public remains low," the USDA, FDA and CDC said on Friday. "Federal and state agencies are moving quickly to conduct additional testing for HPAI, as well as viral genome sequencing, so that we can better understand the situation, including characterization of the HPAI strain or strains associated with these detections."

In:
• Bird Flu
• Agriculture
• Texas
• Kansas

Li Cohen

Li Cohen is a social media producer and trending content writer for CBS News.