Bird flu can live in raw milk for more than a week, study finds

The bird flu virus can remain infectious in raw milk for over a day at room temperature and more than a week when refrigerated, according to a new, non-peer-reviewed research from a group of UK scientists.

The study, published in medRxiv, examined the stability of the H5N1 avian influenza virus in raw cow and sheep milk, with researchers simulating storage conditions common in dairy settings.

“High viral titres were detected in milk from infected cows, raising concerns about onwards human infections,” the authors wrote.

Scientists emphasized that pasteurization effectively kills the virus, but unpasteurized milk poses a potential risk of infection, both through occupational exposure in dairies and the consumption of raw milk.

To test how long the virus remains infectious, scientists incubated the virus in pasteurized milk at room temperature and at 39.2 F, simulating both ambient dairy conditions and refrigerated storage. They also tested sheep’s milk using a lab strain of avian flu.

Scientists stressed that these results represent a “worst-case scenario” and are meant to provide an “upper-bound” estimate of how long H5N1 might survive in milk. They urged continued precautions to reduce zoonotic transmission risks.

Bird flu has devastated poultry and dairy farms, and sent the price of eggs soaring in the U.S. since it was first detected in North America in late 2021.

More than 12,000 individual birds have tested positive since the virus began spreading, according to the Agriculture Department.

The Associated Press contributed to this report.