Can bird flu survive in milk?

Nnow that bird flu is circulating among dairy cattle in at least 12 states in the US and infected three dairy workers, health experts are paying attention to whether people can become infected by consuming infected milk or meat.

Until now, the Union government keeps that the risk of infection is low for the general public and that commercially sold milk remains safe to drink. This is despite the fact that the US Food and Drug Administration (FDA) found that about 20% of milk sold in stores contains fragments of the H5N1 avian influenza virus. However, these fragments are not active so far; the researchers report that they were unable to generate any live viruses from them in the laboratory, and animals exposed to them did not develop infections.

Both agencies also claim that pasteurization, or heating of milk, inactivates the virus. But the timing of pasteurization and the amount of viruses in the milk before it is treated are important in understanding the effectiveness of heat treatment.

In a report Published at the New England Journal of Medicine, researchers from the National Institute of Allergy and Infectious Diseases and the University of California, Los Angeles, wanted to better understand the extent to which the process can inactivate H5N1. They tested raw milk treated at two different temperatures – 63°C (145°F) and 72°C (161°F) – which are typically used to pasteurize milk for retail markets.

see more information: We won’t be protected from bird flu until we protect farm workers

The good news is that at lower temperatures, heat inactivated the virus in raw milk within two minutes – meaning that commercial pasteurization, which typically heats milk to 63°C for 30 minutes, should be enough to inactivate H5N1. . At the highest temperature, the virus was inactivated in most cases after just 20 seconds.

“When we did this study, there was no information about H5N1 in milk because it had never been observed before, so our starting point was to build information on how well these viruses are inactivated by pasteurization,” says Vincent Munster, head of virus ecology. at the Rocky Mountain Laboratories of the National Institute of Allergy and Infectious Diseases. “This is the first study that analyzes the stability, as well as inactivation and heat treatment efficiency of H5N1 in the laboratory.”

While the findings are reassuring that conditions that mimic commercial pasteurization can effectively kill H5N1, the FDA and the U.S. Department of Agriculture are conducting studies to see whether real-world milk treatment processes actually inactivate H5N1. Munster notes, for example, that the effectiveness of pasteurization is time and dose dependent, meaning that milk needs to be treated for a specific period of time, and that milk containing higher concentrations of viruses may require longer exposure. to heat to kill all viruses. Pasteurization facilities often treat milk from farms in multiple states, so batches can contain varying amounts of viruses. Treating them at the same temperatures for the same period of time may not always inactivate all viruses present if the milk contains a high concentration of H5N1. “The next step is to confirm that industrial-scale pasteurization works the way it’s supposed to work,” he says.

For now, it’s important to continue learning more about what happens to the virus as it passes from an infected dairy cow into the milk supply. “Even with very efficient inactivation, H5N1 should not be in our milk,” says Munster. “Therefore, we should make an effort to intensify our countermeasures to prevent H5N1-positive milk from entering dairy processing plants. If we don’t have H5N1 in the milk, we won’t have to inactivate it.”