A recent study found that live bird flu virus (H5N1) can survive in raw milk for over a week when refrigerated, and more than 24 hours at room temperature.
Only unpasteurized (raw) milk is affected—pasteurization effectively kills the virus.
Potential risks exist for people who handle or consume raw milk from infected animals, especially in dairy or farm settings.
Bird flu continues to make headlines – this time, as it pertains to raw milk.
A recent lab study found that H5N1, a highly pathogenic avian influenza virus, can survive in raw milk for quite some time. The study found that the virus stayed alive for over a day at room temperature, and up to a week in the fridge.
“Although the survival of influenza viruses in milk was variable, we consistently found that under laboratory conditions, substantial viral infectivity remained over periods when people might reasonably be exposed to infected milk—for over a day at room temperature and for more than seven days when refrigerated,” the authors wrote.
The study
This UK-based research aimed to explore how long live H5N1 could stick around in real-world milk conditions.
Researchers took raw cow’s milk and sheep’s milk and intentionally added H5N1. They then stored samples at room temperature and in a refrigerator (about 4 °C).
The goal was to mimic how milk might be handled on a dairy farm—left out during milking and then stored in coolers. The researchers explained that this setup represented a “worst-case scenario,” giving an upper-bound for how long the virus might remain infectious in conditions people actually encounter.
The results
Here’s a look at what the researchers found:
At room temperature, the virus stayed infectious for over 24 hours.
In the refrigerator, they could recover a live virus for more than seven days.
This suggests that raw, unpasteurized milk from infected animals could carry the virus long enough to reach consumers—or those working with it.
The study also highlighted this point: pasteurization works. When milk goes through the pasteurization process, the heat inactivates the virus. It’s only a concern when milk is unpasteurized—from either:
Occupational exposure (like dairy workers handling contaminated milk), or
Consumption of raw milk
“Our results highlight the zoonotic risk of H5N1 in raw milk from infected animals, and reinforce the importance of taking measures to mitigate this risk,” the researchers wrote.