Drinking Milk, Raw or Pasteurized, Not Likely to Lead to Bird Flu

For anyone concerned about bird flu and the country’s milk supply, Santa Barbara County health officer Henning Ansorg had some reassuring words: You can’t catch bird flu by drinking milk, raw or otherwise. Splashes of infected milk in the eye is another thing, however.

Food safety became a renewed topic after one brand of raw milk was pulled from grocery shelves on Monday because of H5N1 virus contamination. On Wednesday, a second batch from the same dairy, Raw Farm in the Central Valley, was voluntarily recalled.

Like the first recall, the second sample of raw milk containing live H5N1 virus was found by the Public Health lab for Santa Clara County, a very well-funded department, according to Dr. Ansorg. The California Department of Public Health (CDPH) commented that Santa Clara’s was the only county lab that was conducting tests. The results are verified by a state Food and Agriculture lab, whose personnel have been also testing Raw Farm’s tanks of milk twice a week onsite. Wednesday’s recall is of the farm’s cream top, whole milk, lot code 20241119 with a expiration date of December 7, 2024.

For those who drink milk, raw or pasteurized, or enjoy it in their tea, Ansorg said it was unlikely they’d contract avian influenza by consuming milk products. “There’s really no evidence that drinking milk contaminated with virus would make a human ill,” he said. “Humans only have receptors [for H5N1] in eye tissue and in the lower airways.” Upper airways, like the larynx, lacked the receptors. “The milk would have to be inhaled really deeply, which could happen potentially with aspiration — if it goes down the wrong pipe,” Ansorg added.

However, drinking raw milk is potentially harmful, if only for the other bacteria it can carry, such as E. coli, Listeria, Campylobacter, Salmonella, and others that can make people quite ill. With some raw milk known to be contaminated with H5N1, Ansorg thought it was a risk to drink raw milk: “I don’t think it’s safe.”

In the first recall, Santa Clara County detected H5 virus in one bottle of raw milk from a local grocery store. Santa Clara’s Public Health stated that “One container of raw milk from each of the dairies that sells raw milk in Santa Clara County is tested once per week,” which it has been doing since June. Public Health bought them at retail stores, took samples, and tested them in its lab.

Out of an “abundance of caution,” CDPH had advised consumers to avoid the affected milk. Symptoms of bird flu in humans are eye redness or discharge, flu-like symptoms of cough or body ache, and more serious symptoms of diarrhea, vomiting, and trouble breathing. In cows, signs are low appetite, reduced milk production, and thick, discolored milk. H5N1 is classified “highly pathogenic” for domesticated birds, most often causing death. Wild birds tend to be asymptomatic, according to the Centers for Disease Control.

Symptoms in humans have not been serious so far, Ansorg said, including among diary workers, who’ve come down with conjunctivitis, or eye redness or discharge, and fatigue. “If you see the many cows, they are in milking bays, with a person cleaning the udders and the milking machines. They are sitting or standing at the level of the udder, and it is understandable that they get splashed in their eyes if they don’t wear goggles or the whole protective gear,” he described.

California’s large dairies are in the Central Valley; Raw Farm has somewhere between 750 and 1,000 cows. But locally, the state’s wastewater surveillance network has detected H5 in the sewer streams at Goleta Sanitary District and Lompoc Regional Wastewater Reclamation Plant. The source of the virus — whether human, domestic animal, or wild bird — is unknown.

Over the past few years, H5N1 has spread from continent to continent via migrating birds and waterfowl to sea lions, fox, bears, goats, and other animals, wild and domestic. The virus is transmitted in saliva and feces, and it is known to concentrate in udder tissue, which is why dairy cows are affected, Ansorg said.

The CDC took note in October when a pig was found to have H5N1. It had lived at a backyard farm in Oregon and was the first known case in swine. Most likely infected by the farm’s poultry, the pig’s four siblings were not infected, which calmed the disquiet, as did the fact that the virus had not mutated. In the past, two or more flu viruses infecting a single pig have swapped DNA to create a new virus, sometimes an Influenza A that could spread to humans. An episode like that caused the H1N1 swine flu pandemic in 2009 that is estimated to have caused an early death in about 300,000 people globally.

The risk to the public from H5N1, the CDC states, is currently low.

Editor’s Note: This story added information on December 6, 2024, about the harmful bacteria raw milk can contain in addition to H5N1. Dr. Ansorg clarified that drinking raw milk is strongly not advised.