On March 25, Federal officials announced the detection of a highly pathogenic bird flu virus strain in dairy cows. However, the Food and Drug Administration stated on Friday that initial tests indicate pasteurization effectively eliminates bird flu virus in milk.

However, The avian influenza outbreak in US dairy cattle is spreading rapidly. In just three weeks, the number of states reporting infected cows has increased from six to eight. Additionally, US officials found the H5N1 virus in milk sold in stores, as stated in Wednesday’s media briefing.

Understanding the Bird Flu Virus Outbreak in Cows

USDA confirmed the A(H5N1) virus in 34 dairy herds across nine states. Among them Colorado has been identified as the latest state. Tests showed that one out of every five commercial milk samples in the U.S. contained traces of the virus. H5 bird flu is common among wild birds across the United States. Federal lawmakers are urging the Biden administration to take stronger measures to control the spread of the virus. 

Implications for Human Health and Milk Consumption

Commercially sold milk has been found to contain H5N1 influenza virus particles. But it’s uncertain how the virus is spreading among cattle or if their milk could transmit the infection to humans. Food scientist Diego Diel from Cornell University in New York suggested that finding viral particles in milk sold to consumers indicates that avian flu in cows might be more widespread than initially believed. He emphasizes the importance of increased surveillance and testing in dairies as essential control measures moving forward.

Virologist Brian Wasik from Cornell University suggested also it is a widespread outbreak due to viral material found in commercially sold milk. He explains that infected animals might enter the commercial supply or symptomatic cows could be shedding the virus into milk. It’s also possible that both scenarios are occurring.

US federal rules mandate discarding milk from infected cows. But, it’s unclear if cows can shed the virus before showing symptoms or producing abnormal milk.  Also, FDA mentions that milk from infected cows might appear thicker and yellow than usual. And also, infected animals might eat less and produce less milk. 

Also, considering the Human cases, H5N1 bird flu virus can range from mild, like eye infections or upper respiratory symptoms, to severe illnesses like pneumonia. Also, it can even lead to death in some cases. 

FDA’s Findings on Pasteurization and Milk Safety

To detect H5N1, the FDA utilized a test called quantitative polymerase chain reaction (qPCR), which identifies viral RNA. However, dairy scientist Nicole Martin from Cornell University notes that since the test detects viral genome fragments, it cannot differentiate between live and dead virus remnants.

The FDA announced on Friday that initial PCR tests, considered the gold standard, revealed that pasteurization effectively eradicated the virus in milk and baby formula. Although the FDA didn’t specify the number of products tested, it stated intentions to conduct further testing on 297 products from 38 states.

This additional testing did not detect any live, infectious virus. These results reaffirm our assessment that the commercial milk supply is safe.”

FDA stated

Pasteurization involves heating milk to a specific temperature for a particular duration to kill harmful bacteria that can cause diseases such as listeriosis, typhoid fever, tuberculosis, diphtheria, and brucellosis.

Both pasteurization and the PMO (Pasteurized Milk Ordinance) remain crucial for ensuring milk safety. These are the first studies to examine how effective pasteurization is against the H5N1 virus in bovine milk since it’s the first time this virus has affected cows. The FDA collaborates closely with the CDC’s food safety group and surveillance team to monitor any unusual trends in flu-like illness, flu, or conjunctivitis. 

So far, no unusual trends or activities have been detected. Only one human case associated with exposure to infected cows has been reported. The CDC stated that the risk to the general public is low in connection to this outbreak in dairy cows.

FDA and USDA gather data on H5N1 in dairy cattle, aid state efforts to control the disease. These efforts are ongoing, and results will be shared soon. Based on current information, the FDA and USDA clarified that U.S commercial milk supply remains safe.

Government Response and Safety Measures

Democratic Senator Tammy Baldwin of Wisconsin, a key dairy state, urged USDA to “quickly deploy additional resources in states that have the opportunity to prevent the disease from entering herds.”

The White House has announced that it closely monitors the avian flu situation. Also, they have formed an “immediate response team” to ensure the safety of the nation’s food supply. They aim to monitor trends, mitigate risks, and prevent the virus from spreading.

Starting next Monday, the USDA will mandate that dairy cows test negative for the Influenza A virus at NAHLN-approved labs before interstate transport. According to Bret Marsh, the state veterinarian, Indiana officials consider testing despite no confirmed cases.

We’re taking a look here at the state level to see what we may need to do

Stated Bret Marsh

Lawmakers, including Romney, a Republican U.S. Senator, are working together across party lines to renew the Pandemic and All Hazards Preparedness Act legislation. This law expired last year and aims to strengthen the nation’s ability to respond to pandemics and other public health threats.


In summary, the bird flu outbreak in dairy cows raises concerns about milk safety. Pasteurization is effective, but ongoing research and surveillance are crucial to ensure safety. Collaboration between agencies and states is critical for monitoring and preventing further spread.


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