In the month following the announcement of an outbreak of avian influenza on dairy farms, federal authorities have repeatedly reassured the public that the surge in infections has no impact on the nation's food or milk supply and involves few risks for the population.
Yet the outbreak among cows may be more serious than initially thought. In an obscure online update this week, the Department of Agriculture said there is now evidence that the virus is spreading among cows and from cows to poultry.
North Carolina officials have detected avian flu infections in a herd of cattle without symptoms, the New York Times has learned — information the USDA has not shared publicly. The finding suggests that infections may be more widespread than previously thought.
It's unclear whether there are asymptomatic animals elsewhere, because the USDA does not require farms to test livestock for the infection. It reimbursed farmers for testing, but only for 20 visibly sick cows per farm. This week, the department said it will begin reimbursing farms for testing cows without symptoms.
Federal officials have shared limited genetic information about the virus with scientists and officials in other countries, which is important for learning how the virus might evolve as it spreads.
They are not actively monitoring infections in pigs, which are known to be effective hosts for the evolution of influenza viruses and which are often kept in close proximity to cattle. And officials said they had “no concerns” about the milk's safety, despite a lack of hard data.
In joint statements in March, the USDA, the 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 ascertain whether the process eliminates the virus. The agency declined to say when the results of those tests will be available.
Some experts said the agencies should not have said the milk was safe before they had the data in hand, even if there was only a small possibility of risk to people.
“I understand that the milk market is very concerned about a loss of even a small percentage of milk consumption,” said Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota.
But, he added, “the idea that you can avoid this type of discussion simply by giving absolute values will not serve them well.”
The federal response so far echoes early missteps during the pandemic, he and other experts said. “They appear to have learned little from the communication lessons Covid has taught us,” Dr Osterholm said.
In an interview this week, Dr. Rosemary Sifford, the USDA's chief veterinary officer, said that more than a dozen federal epidemiologists, about double the number of lab employees, field staff members and academic and state collaborators have all been involved in the investigations.
“Please remember that we have been at this for less than a month,” he 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 definitely recognize that we need to know more about the big picture,” he added.
If the department were more forthcoming, 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 and manage it themselves are long gone,” he said.
Part of the problem, some experts say, is that the USDA has long been in a position to regulate and promote farming.
“We all want farms to succeed and we want to have a steady food supply for the American consumer,” said Donn Teske, president of the Kansas Farmers Union. “But then when you also have the task of supervising, it becomes a bit of a problem.”
The current version of the avian influenza virus has been circulating in poultry, wild birds and, more recently, a wide range of mammals since 2020.
As of Friday afternoon, the outbreak in 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 cases of bird-to-cow transmission of the virus, in the Texas Panhandle and New Mexico, Dr. Sifford said.
So far, among cattle, the virus, called H5N1, seems 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 again, from cows to poultry, in at least one case in Texas.
The infected herd and poultry were located on different farms. But according to the Texas Animal Health Commission, the virus may have been transported to each other by people or animals who came into contact with objects contaminated with virus-laden milk.
Infected cows appear to carry large amounts of the virus in their milk. (The USDA has tested relatively few animals by nasal swab, however, and is not testing feces, a common virus repository.)
Milking equipment on dairy farms is generally 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 the H5N1 virus, milk production drops dramatically and the milk becomes viscous and yellowish. “We've never seen something 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 spokesperson for the North Carolina Department of Agriculture.)
In interviews, some experts criticized the USDA's testing recommendations, which until this week promised reimbursement only for a group of obviously sick animals. Farmers may not have found many infections simply because they weren't looking for them.
Widespread testing of animals with and without symptoms is crucial in the early stages of the epidemic to understand the scope and possible mechanisms of viral transmission, said Caitlin Rivers, an epidemiologist at the Johns Hopkins Center for Health Security.
Pigs are a focus in influenza surveillance, many experts have noted, because they are susceptible to both avian and human influenza. They could act as “mixing bowls,” allowing H5N1 to gain the ability to spread efficiently between people.
The USDA is not testing pigs nor is it asking farmers to do so, Dr. Sifford said.
Testing cows for H5N1 infection requires approval from a state official. Milk samples obtained from an accredited veterinarian are typically packaged in tubes, packaged in insulated coolers, and shipped to a USDA-approved laboratory, along with 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 epidemic, 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 without symptoms. The department “strongly recommends testing before herds are moved between states, including asymptomatic herds,” the agency said in a statement.
Already, some state health departments and some farmers have grown frustrated with the federal approach. Several farms in Minnesota — which is not one 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 a current or past infection, the Dr. Joe Armstrong, a veterinarian at the University of Washington. the University of Minnesota Extension.
Other dairy farmers are reluctant to do the testing, worried that fears about avian 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 happen to them than we have gotten samples from,” he said.
Dairy farmers are grappling with low milk prices and high feed costs, said Rick Naerebout, CEO of the Idaho Dairymen's Association.
“The economic situation is already very difficult and thinking about the possibility of losing 20% of revenue for a period of two to four weeks really adds a lot of anxiety to the situation,” he said.
Idaho banned the import of cows from the Texas Panhandle after reports of an avian flu outbreak, but a week late. Having an infected herd in Idaho despite these precautions “was kind of a gut punch,” Naerebout said.
Matt Herrick, a spokesman for the International Dairy Foods Association, said federal officials should provide more resources and equipment to farmers to protect themselves and should publicize the updates more widely, including through social media.
There is no mention of the avian flu outbreak on the USDA homepage. The latest outbreak announcement from the Animal and Plant Health Inspection Service, a division of the department, was dated April 2.
The USDA is exploring vaccines to protect livestock from H5N1, but it's unclear how long it might take to develop them. Dr. Armstrong, of the University of Minnesota Extension, said many farmers and veterinarians hope the virus “runs out.”
Instead, it could become a long-term problem. “The goal is to prepare for this,” she said. “Not by this wishful thinking, 'it will go away.'”