In the month since federal authorities announced an epidemic of bird flu on dairy farms, they repeatedly reassured the public that the wave of infections was not impacting the country’s food or dairy supply and posed little risk to the public.
Still, the outbreak in cows may be more serious than initially thought. In an obscure online update this week, the Agriculture Ministry said there is now evidence that the virus is spreading between cows and from cows to poultry.
Authorities in North Carolina have detected avian flu infections in a herd of cattle showing no symptoms, The New York Times has learned — information the USDA has not shared publicly. These findings suggest that infections may be more widespread than previously thought.
It remains unclear whether there are asymptomatic animals elsewhere because the USDA does not require farms to test cattle for infection. It reimbursed farmers for testing, but only for 20 cows per farm that were visibly sick. This week, the ministry announced it would begin reimbursing farms that test cows without symptoms.
Federal officials have shared limited genetic information about the virus with scientists and officials in other countries, which is important for understanding how the virus might evolve as it spreads.
They do not actively monitor infections in pigs, which are known to be effective hosts for evolving influenza viruses and are often raised in close proximity to cattle. And the officials have said they have “no concerns” about the safety of milk, despite the lack of concrete data.
In joint statements in March, the USDA, Food and Drug Administration and the Centers for Disease Control and Prevention assured the public that pasteurized milk was safe. But the FDA is still conducting tests to see if the process eliminates the virus. The agency declined to say when the results of those tests would be available.
Some experts said the agencies should not have claimed the milk is safe before having the data in hand, even if there is only a small chance of harm to people.
“I understand that the milk market is very concerned about a loss of even a few percent of milk consumption,” said Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota.
But, he added, “the idea that we can avoid this kind of discussion by simply giving absolutes will not be very useful to them.”
The federal response so far echoes early missteps of the pandemic, he and other experts said. “It seems they have learned little of the communication lessons that Covid has taught us,” Dr. Osterholm said.
In an interview this week, Dr. Rosemary Sifford, USDA’s chief veterinarian, said more than a dozen federal epidemiologists, about twice as many laboratory workers, field staff and university and state collaborators, were all involved in the investigations.
“Remember, we’ve been working on this for less than a month,” she said. “We are working very hard to generate more information.”
USDA staff are only analyzing viral genetic sequences from diseased cows, but will release information for outside experts “in the very, very near future,” Dr. Sifford said.
“We certainly recognize that we need to learn more about the bigger picture,” she added.
If the department were more open, scientists outside the government could already help contain the virus, said Dr. Tom Inglesby, director of the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health.
“The days when it was considered a good plan or acceptable for a government agency to keep all the data to manage it themselves are long gone,” he said.
Part of the problem, some experts say, is that the USDA has long been in the position of regulating and promoting the agricultural sector.
“We all want farms to succeed and we want to have a stable food supply for the American consumer,” said Donn Teske, president of the Kansas Farmers Union. “But when you’re also tasked with monitoring, that poses a bit of a problem.”
The current version of the avian influenza virus has been circulating since 2020 in poultry, wild birds and more recently in a wide range of mammals.
By Friday afternoon, the outbreak among dairy cows had spread to 32 herds in eight states: Texas, New Mexico, Michigan, Kansas, Idaho, Ohio, North Carolina and South Dakota.
It is unclear how the outbreak began on dairy farms. Early data suggests there have been at least two bird-to-cow transmissions of the virus, in the Texas Panhandle and New Mexico, Dr. Sifford said.
So far in cattle, the virus, called H5N1, appears to only affect lactating cows, and only temporarily. There were no diagnoses in calves, pregnant heifers or beef cows, and no deaths. But the virus appears to have spread from cows to poultry, in at least one case in Texas.
This infected flock and flock of poultry were on different farms. But the virus could have been carried between them by people or animals who had contact with objects contaminated by virus-laden milk, according to the Texas Animal Health Commission.
Infected cows appear to carry large amounts of the virus in their milk. (The USDA, however, has tested relatively few animals by nasal swab and does not test feces, a common repository for viruses.)
Milking equipment on dairy farms is usually thoroughly cleaned, but not sterilized, at least once a day. People who milk cows are encouraged to wear safety glasses, masks or face shields, but the recommendations are often ignored.
In cows infected with H5N1, milk production decreases sharply and the milk becomes viscous and yellowish. “We’ve never seen anything like this before,” said Dr. Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory.
(Milk from infected but asymptomatic cows appears unchanged, according to a spokeswoman for the North Carolina Department of Agriculture.)
In interviews, some experts have criticized the USDA’s testing recommendations, which until this week promised reimbursement only for a group of obviously sick animals. Farmers may not have detected many infections simply because they weren’t looking for them.
Widespread testing of animals with and without symptoms is essential early in outbreaks to understand the extent and possible mechanisms of viral transmission, said Caitlin Rivers, an epidemiologist at the Johns Hopkins Center for Health Security.
Pigs are a critical part of flu surveillance, many experts noted, because they are susceptible to both avian and human flu. They could act as “mixing bowls,” allowing H5N1 to gain the ability to spread effectively among humans.
The USDA doesn’t test pigs or ask farmers to do so, Dr. Sifford said.
Testing cows for H5N1 infection requires approval from a state official. Milk samples obtained by an accredited veterinarian are typically packaged in tubes, in insulated coolers, and shipped to a USDA-approved laboratory, accompanied by a unique identifier. Positive tests are then confirmed by the USDA National Laboratory in Iowa.
Each step slows the rapid response needed to contain an outbreak, Dr. Inglesby said. Testing should be easy, free and accessible, he said.
Dr. Sifford said the USDA has already received a “small number” of samples from cows showing no symptoms. The department “strongly recommends testing before herds are moved interstate, which includes asymptomatic herds,” a statement from the agency said.
Some state health departments and farmers are already frustrated with the federal approach. Several Minnesota farms — none of the eight states with known cases — are sending cow blood samples to private labs to test for antibodies to the virus, which would indicate current or past infection, said veterinarian Dr. Joe Armstrong at the University of Minnesota Extension.
Other dairy farmers are reluctant to test, fearing that fears about bird flu could hurt their business, said Dr. Amy Swinford, director of the Texas A&M Veterinary Medical Diagnostic Laboratory.
“I think there are a lot more dairies that have had this problem than the ones we’ve gotten samples from,” she said.
Dairy farmers are struggling with low milk prices and high feed costs, said Rick Naerebout, executive director of the Idaho Dairymen’s Association.
“It’s already a very difficult economic situation, and to consider losing 20 percent of your income for a period of two to four weeks — it really adds a lot of anxiety to the situation,” he said.
Idaho banned the importation of cows from the Texas Panhandle after news of a bird flu outbreak there, but a week too late. Having an infected herd in Idaho despite these precautions “was kind of a gut punch,” Mr. Naerebout said.
Matt Herrick, a spokesman for the International Dairy Association, said federal authorities should provide more resources and equipment for farmers to protect themselves, and should disseminate updates more widely, especially via social networks.
There is no mention of the avian flu outbreak on the USDA homepage. The last announcement about the outbreak from the Animal and Plant Health Inspection Service, a division of the department, was made on April 2.
The USDA is explore vaccines to protect livestock from H5N1, but it is unclear how long it will take to develop them. Dr. Armstrong, of the University of Minnesota Extension, said many farmers and veterinarians are hoping the virus “will die out.”
Instead, it could become a long-term problem. “The goal is to prepare for that,” he said. “Not for this wishful thinking like, ‘It’ll just go away.’ » »
