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Helen Chu
May 1, 2024

Infectious-diseases expert addresses bird flu concerns

Despite the novel outbreak among U.S. dairy-cow herds, pasteurized milk should be safe to drink, Dr. Helen Chu says.
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Avian influenza H5N1 is a virus that mostly affects poultry and wild birds, but the U.S. outbreak of bird flu among dairy herds, and one documented human infection, are raising Americans’ concerns about potential health dangers. 

Dr. Helen Chu, an infectious-diseases expert at UW Medicine in Seattle, discussed the risk of humans contracting bird flu and the safety of drinking dairy cow milk and eating beef and eggs.

“The lab tests that are being done are molecular tests, so they are very sensitive,” Chu explained. “They will pick up very small amounts of the virus. These tests will be positive if there are fragments of the virus. We do not yet know whether there is evidence that there is living virus in the milk or the beef, and even so, if the amount is enough to cause infection.”

Proper food handling should safeguard families. “Beef and eggs, if cooked thoroughly, should be fine to eat because the process of cooking food at high temperatures will destroy the virus,” she said. 

“What we know about avian flu is that it's not well adapted to cause infection in humans. The reason for that is because, in birds the virus attaches to certain receptors in the airways … and we don't share those same receptors,” she said. “Mammals like cows are not supposed to get sick with avian influenza, but obviously that's not what we’ve been seeing.”

Amid the current livestock outbreak, a Texas dairy worker is the only person with a documented H5N1 infection. That person’s virus was genetically sequenced and found to have had one adaptation that allows it to transmit more easily to mammals, Chu said. But multiple mutations would be needed for H5N1 to become “highly transmissible” in mammals, she added, “and there's currently no evidence that there is transmission person to person.” 

Chu also said she thinks dairy cow milk is safe to consume. 

“I think it's fine because what they're finding right now are really just the fragments of the virus, dead virus, in the milk. They found no evidence of live virus in the milk. And even if it was originally live in the milk, that process of pasteurization should kill it,” she said.