With the H5N1 bird flu virus racing through California dairy herds, the U.S. Department of Agriculture announced Friday it is instituting a mandatory milk testing program that should provide a much clearer picture of how widespread the virus is in the country’s dairy industry.
Nearly nine months after the outbreak in dairy cows was first detected, the USDA announced it will start to require farms to provide milk for testing when asked. The program will begin with six states, California, Colorado, Michigan, Mississippi, Oregon, and Pennsylvania. Other states will be added later. Of the initial group, California, Colorado, Michigan, and Pennsylvania are already doing bulk tank testing on dairy farms.
The statement announcing the new federal order indicated the move will help inform the response to the outbreak, and assist farmers and farmworkers to protect themselves from infection.
It does not reveal, though, whether the information gathered will be released to the public, or how frequently, if it is to be released. STAT reached out to USDA to ask whether the information the department amasses will be disclosed, but has not yet received an answer.
As of Friday, the USDA had confirmed 720 herds in 15 states have had infected cows since the outbreak was first detected at the end of March. The vast majority — 506 — have been in California, which has been actively looking for infections, both among herds and among people, since its first affected herds were detected in late August. Many states, including some of the country’s top dairy producers, have reported no infected herds — though whether that represents a lack of infections or a lack of testing hasn’t been clear.
“Among many outcomes, this will give farmers and farmworkers better confidence in the safety of their animals and ability to protect themselves, and it will put us on a path to quickly controlling and stopping the virus’ spread nationwide,” Agriculture Secretary Tom Vilsack said in a press release.
The U.S. response to the outbreak in cows has been widely criticized by influenza experts at home and abroad who see the continued circulation of the virus in mammals — mammals with which humans come in regular contact — as playing with fire. H5N1 is a virus that is suited to infecting wild birds; while sporadic human infections have occurred, the virus doesn’t currently have the capacity to spread easily to and among people. If it acquired the mutations that would allow it to do so, it is believed the virus would trigger a pandemic.
A study published Thursday in the journal Science suggested that this version of the virus might have an easier time mutating to allow for human-to-human transmission than earlier iterations of H5N1. Scientists from Scripps Research in La Jolla, Calif., reported that a single change at a key position on the hemagglutinin, the main protein on the virus’ surface, allows it to attach easily to cells in the human upper airways.
In the nearly 30 years since H5N1 was first detected in China, roughly 1,000 human infections have been detected. Of those, just under 50% have been fatal.
Prior to this year, the United States had only ever recorded one human case, in April 2022, in a person who was involved in culling poultry on a Colorado farm battling an H5N1 outbreak. But this year alone the country has recorded 58 cases, most in dairy farmworkers or poultry cullers. Two of the cases, though, were in people for whom a source of infection could not be identified.
Critics have questioned why the USDA hasn’t more aggressively tried to detect where the virus is spreading in cows. The goal, they have insisted, should be to get the virus out of the cow population. But the fact that the virus rarely kills cows has worked against this effort. Many farmers believe it is not a big deal, and have resisted efforts to locate infected herds. The USDA’s efforts to date have not been as proactive as experts believe they would need to be to stop the spread in cows.
Testing has shown that raw milk from cows infected with H5N1 contains extraordinarily high levels of virus. It’s not known if people can become infected by drinking virus-laced milk, but studies have shown that mice fed raw milk became so ill they had to be euthanized. And there have been multiple reports of dead cats on affected farms.
But studies conducted by the Food and Drug Administration and others have shown that pasteurization kills the virus.
The new federal order allows USDA to obtain raw milk samples from any player in the production and distribution network. It also requires herd owners found to have positive cattle to provide information that would allow the agency to trace the source of the virus and follow movement of cows. And it reiterates a requirement from an earlier order that private laboratories and state veterinarians that detect positive cows must report them to the USDA.
