The Centers for Disease Control and Prevention (CDC) warns that the A(H5N1) virus has been detected in raw, unpasteurized milk from cattle infected with the virus. The agency recommends that consuming raw milk can be dangerous, and that people should always drink pasteurized milk, especially now with the uncertainty of the virulent avian flu that has spread to herds of dairy cattle.

According to Barron's, the World Health Organization (WHO) expressed concern that the virus was found in “very high concentrations” in raw milk, although experts don’t know how long the pathogen can survive in milk. The strain of bird flu that first emerged in 1996 caused more outbreaks since 2020 and infects not only birds, but also mammals.

Eight U.S. states have been affected by the A(H5N1) virus causing occurrences in dairy cattle and has spread between herds and nearby poultry farms. So far, only one human case has been identified with bird flu and involved a dairy worker in Texas who reported eye redness from contracting the highly contagious virus. He is recovering.

Dr. Jeremy Farrar, chief scientist at the WHO, said the strain of flu has an “extremely high” mortality rate among those infected, according to the New York Post. He expressed concern that as the virus evolves, it may increase its ability to go from human-to-human transmission.

For now, the threat of contracting the avian flu from drinking milk is confined to raw or unpasteurized products. Drinking raw milk, in general, is a bad idea because it may carry other pathogens like salmonella, listeria and E. coli. Pasteurized milk, the kind that is available in grocery stores, remains safe. Dairy farms in the U.S. are required to destroy milk from infected animals so it doesn’t make it into the food chain in the first place.

The WHO urged U.S. officials to monitor the situation closely to prevent an escalation of transmission that could eclipse the SARS-CoV-2 pandemic.

“Do the milking structures of cows create aerosols? Is it the environment in which they’re living in? Is it the transport system that is spreading this around the country?” Farrar asked. “This is a huge concern.” Farrar said that officials need to ensure that the virus does not evolve into human-to-human transmission and that we need to be ready with appropriate vaccines, therapeutics, and diagnostics in the eventuality that it does become a threat.

The death rate in humans may be upwards of 50%, according to data from WHO. By comparison, COVID-19 currently kills less than 0.1% of infected people. Experts warn that the bird flu situation could be “100 times worse than COVID-19.”

Wenqing Zhang, head of the global influenza program at WHO, says that the human cases reported in Europe and the U.S. so far have been mild since the surge. She says there are vaccines available, and some more are in the pipeline.

“For this particular H5N1 virus detected in dairy cows, there are a couple of candidate vaccines available,” she said, according to Barron’s.

But while the current risk of infection to the general public remains low, says the CDC, people who have close or prolonged, unprotected exposures to infected birds or other animals, or to environments that are contaminated by infected birds or other animals, are at greater risk of infection.