Mice Became Sick from Raw Milk Contaminated with Bird Flu Virus in Experiments

Researchers have confirmed the dangers of drinking raw cow’s milk during an outbreak of the H5N1 avian flu virus in U.S. dairy herds. A study led by virologist Yoshihiro Kawaoka from the University of Wisconsin-Madison found that mice fed raw milk contaminated with the virus quickly became ill.

The researchers first detected traces of the H5N1 bird flu virus in nasal swabs and milk obtained from U.S. dairy cows in late March. Since then, the outbreak has spread to many dairy herds across multiple states. While there have been only two known human cases of H5N1 infection linked to the outbreak, both cases occurred in dairy workers who had prolonged, close contact with the animals.

Experts believe that the general milk supply is safe due to pasteurization, which kills the virus. However, consuming unpasteurized “raw” milk poses a risk of transmitting H5N1 to other mammals, including humans.

In the study, mice fed raw cow’s milk contaminated with H5N1 showed signs of infection within a day, such as ruffled fur and lethargy. The researchers found high levels of the virus in the respiratory organs and moderate levels in other organs, indicating systemic infection.

Refrigerating the infected milk at 39 degrees Fahrenheit for five weeks did not eliminate the virus completely, suggesting that it can remain infectious for several weeks. Pasteurization reduced virus levels to undetectable or barely detectable levels, emphasizing the importance of heat-treating milk to prevent infection.

The researchers stressed the dangers of consuming raw milk, citing previous studies linking raw milk consumption to hospitalizations, deaths, and illnesses. Kawaoka’s message is clear: “Don’t drink raw milk.”