Bird flu virus has been found in a batch of raw -- unpasteurized -- milk sold in California, prompting a recall issued at the state's request, health officials announced over the weekend.
No illnesses have yet been linked to the contaminated milk, made by Raw Farm, LLC of Fresno County. The contamination was found in testing by health officials in nearby Santa Clara County, who detected the virus in milk from a retail store. The state laboratory has confirmed the finding.
In a YouTube message from Raw Farm, a company representative called the contamination "not a big deal" and emphasized that the recall is only being done out of an abundance of caution.
The detection of bird flu in retail raw milk is troubling but not surprising given the unprecedented and ongoing outbreak of H5N1 bird flu among US dairy cows, which is currently soaring in California, the country's largest dairy producer. Since the virus was first detected in state herds in late August, California has tallied 402 infected herds, which is among the country's 616 total across 15 states since March. Further, California has reported 29 confirmed human cases of bird flu, 28 of which had direct contact with infected dairy cows. The US has reported a total of 55 human cases.
It's not entirely clear how dangerous it is for humans to ingest avian influenza virus in contaminated milk; typically, people are infected by human influenza viruses through the spread of respiratory droplets. But researchers and regulators consider bird flu-containing milk a clear biohazard.
In cows, the bird flu appears to especially target the mammal's mammary glands, and studies have found that the milk of bird flu-infected cows is brimming with high levels of infectious virus. In a study published in the New England Journal of Medicine in May, mice fed raw milk contaminated with bird flu became severely ill. Further, there have been numerous reports of farm cats on H5N1-infected dairies developing brain infections, blindness, and dying in high numbers after drinking infected milk. It's unclear if humans would follow the same course.
Of the human H5 cases detected in the US so far this year, all have been mild, and nearly all have been from direct exposure with infected animals. Earlier this month, Canada reported its first case of H5 bird flu in a human: a teen in critical condition with no clear exposure to infected animals. According to the World Health Organization, there were 905 H5N1 cases globally between January 2003 and September 27, 2024. Of those cases, 464 were fatal, with a case fatality rate of 51 percent.