The U.S. Food and Drug Administration (FDA) on April 23 said that particles of avian influenza have been found in milk from grocery stores, indicating the highly pathogenic virus has made its way into America’s commercial milk supply.
“Based on available information, pasteurization is likely to inactivate the virus, however the process is not expected to remove the presence of viral particles. Therefore, some of the samples collected have indicated the presence of HPAI using quantitative polymerase chain reaction (qPCR) testing,” the agency said.
While samples tested positive, that does not mean they contain an intact pathogen, according to the FDA.
“Additional testing is required to determine whether intact pathogen is still present and if it remains infectious, which determines whether there is any risk of illness associated with consuming the product,” it said.
The agency is injecting samples into fertilized chicken eggs to see whether any active virus replicates, among other experiments. It is also completing testing on samples taken from pasteurized milk from across the nation.
“To date, we have seen nothing that would change our assessment that the commercial milk supply is safe. Results from multiple studies will be made available in the next few days to weeks,” the FDA said.
The agency did not immediately respond to a request for comment for more details, including how many samples tested positive and which stores the milk that tested positive came from.
The announcement comes nearly a month after the avian influenza virus was first detected in U.S. dairy cows. The virus has sickened millions of wild and commercial birds in recent years.
Yaneer Bar-Yam, president of the New England Complex Systems Institute, said on the social media platform X the findings mean “milk from sick cows is being used” in the commercial supply. While pasteurization likely makes the milk safe, that safety is “not guaranteed.”
Angela Rasmussen, a virologist, said that the positive samples “suggests there are undetected herds shedding virus into the milk supply” because they show intact virus “was once present.”
“It’s hard to say more as no raw data was shared, so we just have to take their word for it,” she added.
U.S. authorities previously said that milk from diaries with sickened animals was “being diverted or destroyed so that it does not enter the food supply” and that “pasteurization has continually proven to inactivate bacteria and viruses, like influenza, in milk.” The FDA acknowledged in the new update that while pasteurization is an effective process, “no studies on the effects of pasteurization on HPAI viruses, such as H5N1 in bovine milk have previously been completed.” The federal agency is relying on “considerable scientific literature” to inform its policy and decision-making, it said.
Currently, highly pathogenic avian influenza has infected 33 herds of livestock in eight states: Idaho, New Mexico, Texas, South Dakota, Kansas, Michigan, Ohio, and North Carolina. All affected livestock are dairy milking cattle. Cows that become infected typically tend to produce less milk and have low appetites, the FDA reported.
The FDA said the agency is taking precautions to ensure the effectiveness of the federal-state milk safety system. For example, a food safety group from the FDA and U.S. Centers for Disease Control and Prevention (CDC) are working together to survey and monitor department data. In particular, they are searching for anomalies in flu-like illnesses, including conjunctivitis. To date, no anomalies have been reported.
Human infections with the avian bird flu are rare, the CDC reports. The risk of infection increases for individuals who have unprotected exposure to any infected animal or to an environment in which infected birds or animals have been present.
A dairy worker in Texas who had close contact with an infected cow developed a mild eye infection in early April. For the most part, human infections have been sporadic, with no human-to-human transmissions recorded.
The CDC recommends that individuals who work in those environments protect themselves by wearing personal protective equipment.
The general public can protect itself by avoiding raw milk and raw milk products, which do not go through pasteurization.
