Unexpected Threat to Raw Milk Safety Discovered in Dairy Cows

Concerns over raw milk safety have surged with studies revealing the presence of H5N1 bird flu in dairy cows.

At a Glance

Mice given raw milk from H5N1-infected dairy cows showed high virus levels.
The study raises concerns about potential human risk from raw milk consumption.
H5N1 has circulated in 23 countries, primarily affecting wild birds and poultry.
Recently, the virus spread to dairy cows in the U.S., affecting 52 herds.
The FDA advises against drinking raw milk and promotes pasteurization.

Raw Milk Safety Concerns

The detection of H5N1 bird flu in dairy cows has sparked serious public health concerns about raw milk consumption. Research shows that cows can excrete the virus in their milk if udders become infected during milking. The virus poses little risk from respiratory spread but significant risk through milk contamination.

Mice given raw milk from H5N1-infected cows exhibited high virus levels in respiratory organs and lower levels in other organs. This research highlights a potential risk to humans who consume such milk.

Since 2003, H5N1 has predominantly affected wild birds and poultry, with about 900 cases of human infection worldwide. Recently, H5N1 has spread to over 50 animal species, including dairy cows in the U.S., where 52 cattle herds have been affected across nine states, and two human infections detected.

A new study published today in @JVirology shows H5N1 bird flu was found in dairy cows and raw milk, but pasteurized milk is safe: https://t.co/nbARLkfPoh

— ASM Newsroom (@ASMnewsroom) July 3, 2024

Transmission and Testing

Studies indicate that raw milk stored at 4℃ for five weeks shows only a small decline in virus levels, suggesting the virus remains infectious at refrigerated temperatures. The FDA has concluded that the commercial milk supply is safe, as an initial survey of retail dairy products showed no viable virus. However, USDA tests have found the virus in samples of unpasteurized milk.

This situation has caused tensions between the federal government and raw milk advocates. Public health officials recommend pasteurization to inactivate the virus and advise against consuming raw milk. Yet raw milk remains accessible in many areas, and some farms, particularly in Texas where the bird flu was first detected in cows, have declined to have their raw milk tested.

It’s rare, but #H5N1 #birdflu can infect people. Take precautions working with poultry, dairy cows, or unpasteurized (raw) milk. Find out how you can reduce your risk if you work around animals that could be infected at https://t.co/nxf4gUvpoL pic.twitter.com/vTNN9ykJQ4

— CDC Flu (@CDCFlu) July 19, 2024

Advisories and Recommendations

USDA tests have found the virus in samples of unpasteurized milk, raising public health alarms. The FDA advises against the manufacture or sale of raw milk or raw milk cheese from cows showing symptoms of illness. “Pasteurization is effective at inactivating the virus,” said Don Prater, head of the FDA’s Center for Food Safety and Applied Nutrition.

Despite health officials’ warnings, raw milk advocates argue that the risks are exaggerated. The tension between raw milk proponents and federal authorities continues, with the FDA finding bird flu virus fragments in 20% of pasteurized grocery store samples—though these were not capable of causing infections.