Food and Drug Administration officials reported this week that laboratory tests found genetic material from H5N1 strains of bird flu in samples of store-bought pasteurized milk. Officials say these samples do not appear to contain live viruses and that the commercial milk supply should still be safe. However, the results suggest that the virus has spread more widely on dairy farms than previously thought.
Researchers discovered H5N1 in store-bought milk using a highly sensitive quantitative polymerase chain reaction (qPCR) test, which looks for traces of genetic material belonging to a target germ. Importantly, these tests cannot be used to confirm the presence of a live, infectious virus. The FDA’s initial assessment is that these tests only identified inert remnants of H5N1 in the milk. But the agency is now preparing to conduct additional “gold standard” tests to be sure. At the same time, health authorities continue to believe that commercial milk is unlikely to contribute to the spread of H5N1 to humans.
“The FDA and USDA have indicated that based on currently available information, our commercial milk supply is safe for these two reasons: 1) the pasteurization process and 2) the diversion or destruction of milk from sick cows,” the agency said said Tuesday in its latest update on the situation.
To date, cases of highly pathogenic H5N1 in cows have been identified on at least 30 farms in eight states. These strains are considered highly pathogenic because they can cause massive illness and death in wild and domestic birds. So far, infected cows have generally avoided severe illness, but many have experienced symptoms such as reduced or discolored milk production and loss of appetite. There have also been cases of H5N1 found in cats that have been linked to these farm outbreaks, along with at least one human case, although no deaths have been reported in either species.
Genetic evidence was made available to the outside scientific community on Sunday suggests that the first spillover event from birds to cows may have occurred as early as December 2023, months before The first known cases were reported by local officials. And along with the discovery of H5N1 in purchased milk, it is now likely that outbreaks are much more widespread than currently thought.
“The prevalence in cows is far greater than we are led to believe,” said Eric Topol, founder of the Scripps Research Translational Institute. told CNN on Tuesday.
The biggest concern with bird flu strains like H5N1 is that they could one day develop the right mutations that would allow the virus to spread easily between people while causing serious illness in many people. So the longer it is able to remain in cows, the greater the likelihood that some strains will adapt and become better able to transmit between mammals, including humans.
Even if our milk supply is secure, the overall risk to humans remains low for nowThese recent developments suggest that it won’t be easy to nip H5N1 in the bud before it gets worse.