Federal agencies with competing interests are slowing the country’s ability to track and control an outbreak of highly virulent bird flu that for the first time is infecting cows in the United States, according to government officials and health and industry experts.

The response has echoes of the early days of 2020, when the coronavirus began its deadly march around the world. Today, some officials and experts express frustration that more livestock herds aren’t being tested for avian flu, and that when tests and epidemiological studies are conducted, results aren’t shared fast enough or with enough detail. They fear that the delays could allow the pathogen to move unchecked — and potentially acquire the genetic machinery needed to spread swiftly among people. One dairy worker in Texas has already fallen ill amid the outbreak, the second U.S. case ever of this type of bird flu.

Officials and experts said the lack of clear and timely updates by some federal agencies responding to the outbreak recall similar communication missteps at the start of the coronavirus pandemic. They point, in particular, to a failure to provide more details publicly about how the H5N1 virus is spreading in cows and about the safety of the milk supply.

“This requires multiple agencies to coordinate and communicate internally, but most importantly externally, which doesn’t seem to be happening due to different cultures, priorities, legal responsibilities, scientific expertise, and agility,” said Katelyn Jetelina, an epidemiologist who writes a weekly infectious-diseases newsletter and has closely tracked the avian flu outbreak. “Mix that in with the usual challenges of scientific uncertainty, complexity and, quite frankly global pressure, and you got yourself an utterly, unacceptable mess.”

A senior administration official said there have been “no competing interests.” The White House’s Office of Pandemic Preparedness and Response Policy is coordinating the outbreak response with relevant agencies “that are working quickly and methodically.” The government is “committed to sharing results as soon as possible,” said the official, who spoke on the condition of anonymity to discuss internal deliberations.

“This work is an urgent priority as we work to ensure the continued effectiveness of the federal-state milk safety system and reinforce [the Food and Drug Administration’s] current assessment that the commercial milk supply is safe,” the administration official said.

Until Wednesday, testing for H5N1 in dairy herds was voluntary and limited to cows with certain symptoms. The number of tests per farm was limited, too. That protocol provoked sharp criticism from public health experts. With growing evidence that the virus is more widespread than feared among cows, the U.S. Agriculture Department announced Wednesday that lactating dairy cows must be tested for bird flu before moving across state lines, starting Monday.

Responsibility for monitoring and containing the outbreak is divided among three agencies. USDA leads the investigation into the virus in cows, the FDA oversees food safety, and the Centers for Disease Control and Prevention is monitoring risks to people.

Agencies have given individual updates on their parts of the outbreak investigation, but Wednesday marked the first time since bird flu was detected in cows four weeks ago that CDC, FDA and USDA, along with other agencies, held a news briefing jointly. On Thursday, government scientists are scheduled to present data about their investigations at a webinar hosted by state health officials.

For weeks, key federal agencies have expressed confidence in the safety of the commercial milk supply, including pasteurized products sold at grocery stores.

But it was two weeks before the FDA responded directly to The Washington Post’s questions about whether the agency was testing milk on grocery store shelves for H5N1. On Tuesday, the agency confirmed that viral particles had been found “in some of the samples,” but it declined to provide details. On Wednesday, an FDA official confirmed fragments were found in milk on shelves but declined to say how many samples the agency has tested, how many had virus fragments and where the milk originated. The testing does not indicate whether virus fragments are active or dead.

Additional testing is underway, but Donald A. Prater, acting director of the FDA’s Center for Food Safety and Applied Nutrition, said the agency has seen nothing to change its assessment that the commercial milk supply remains safe. “We also know that assessments can change as we learn more, and we will be transparent about any changes based on emerging data,” Prater said.

Officials are seeking answers to other key questions: They want to know whether the virus is spreading among cows through mechanical means, such as milking equipment, as evidence suggests, or through the air, which would be more dangerous and lead to more sustained spread. They are also interested in knowing how long livestock will shed virus in their milk once they have recovered from an infection. And, crucially, they will seek to ascertain the risks for human exposure and whether protocols are in place at the state level if additional people test positive.

The investigation “involves different types of samples, different types of studies and really being methodical about how we’re approaching answers to those questions around things like ensuring safety of the food supply,” said one senior government official who spoke on the condition of anonymity to share internal policy discussions.

“We’re not trying to pull the fire alarm here and suggest that there’s more of a risk to people than exists,” said another federal health official, who also spoke on the condition of anonymity to share internal deliberations.

The key to the outbreak resides with the cows.

Public health officials and industry experts say the USDA should be doing broader testing to paint a clearer picture of the scale of the outbreak. The government has been too slow in sharing genetic information and epidemiological studies, they said. More routine testing on herds and even other animals would reduce the risk of spreading the virus to other cattle and poultry farms, public health experts and veterinarians have said.

“Given this is a novel outbreak, testing needs to be done widely and rapidly, investigators need to be on affected farms, and scientists and policymakers need to be bringing it all together to set a coordinated plan of action,” Tom Inglesby, director of the Johns Hopkins Center for Health Security, said in an email last week. Inglesby was the White House testing czar during the Biden administration’s coronavirus response.

“This isn’t just about protecting U.S. agricultural interests,” said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. “This is about protecting human health, protecting farmworkers that may be in harm’s way and preventing another pandemic from happening.”

Nearly three dozen livestock herds in eight states have been infected in the last month. The virus has also spread from dairy farms to poultry farms and infected barn cats. Epidemiologists fear that indicates cows can pass the virus to birds, and possibly other animals, broadening the potential for spread.

Scientists who performed genetic analyses of virus taken from infected animals say the tests suggest the outbreak may have been occurring for longer and across more of the United States than previously thought.

Michael Worobey, a University of Arizona virologist who led a team of scientists who analyzed 239 genetic sequences released Sunday by the USDA, said the evolutionary tree of the virus “resoundingly indicates that this outbreak had a single origin and that it had been circulating under our noses for months before it was noticed.”

“The concerning thing was it meant that all of these outbreaks in at least eight different states traced back to a common ancestor that had been around probably since late 2023 and that meant that this outbreak almost certainly has its tendrils all across the U.S. and perhaps beyond,” Worobey said.

Scientists trying to piece together the outbreak’s genesis said the USDA was too slow in sharing critical genetic data initially, and when “a big dump” of 239 genetic sequences arrived Sunday, it was not comprehensive.

“Like what samples they are coming from, when exactly they were collected … and where exactly they were collected,” said Angela Rasmussen, a virologist and principal research scientist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada.

Public health and veterinary experts say they also want more epidemiological data — including information on the movement of animals, their feed sources and how many workers are on-site — to understand how and where the virus is circulating.

Beth Thompson, South Dakota’s state veterinarian and president of the National Assembly of State Animal Health Officials, said such information needs to be shared quickly.

“It’s like if you just rip one page out of a chapter in a book and hand it to the states, that isn’t the whole chapter,” Thompson said. “We need all of the information to be given back to us.”

The lack of more aggressive testing of livestock and transparent data-sharing has frustrated officials at the Department of Health and Human Services, according to another federal health official and a public health expert who were briefed on the response.

USDA officials may be constrained by their mission to promote new markets for farmers and protect animal health and welfare, said an administration official who spoke on the condition of anonymity to discuss internal deliberations. “They’re just twisting themselves into knots because they’ve got two missions that are, in this instance, pointing in different directions,” the administration official said.

The official suggested the agency is operating at a level of urgency closer to a 4 when it should be a 10, the official said.

Not true, said USDA spokeswoman Marissa Perry.

“USDA’s top priority is containing this emerging animal health issue,” Perry said.

While H5N1 is typically fatal in poultry, the disease in infected cows has been relatively mild, and animals have recovered in a week to 10 days, according to agriculture officials.

The biggest challenge so far has been identifying farms willing to share samples, said Rosemary Sifford, the USDA’s chief veterinary officer. The agency has been testing sick and healthy cows in affected herds, and in recent days began testing in unaffected herds, she said in an interview last week.

The virus appears to be spreading in cows that are producing milk “and the place that those animals are most closely congregated, have the most contact, would be as they’re moving through the milking parlor,” Sifford said. “We are not seeing this virus moving outside the lactating herd.”

This strain of avian flu has been circulating for more than 20 years, but its leap into cows is of significant concern, surprising even longtime observers of the virus. While avian flu has infected humans — especially in Asia — the virus has yet to prove able to spread efficiently in people. But the more the virus jumps animal to animal, the greater the chance mutations will emerge that allow sustained person-to-person transmission, the required next step for a pandemic.

State health officials have tested at least 23 people; only the dairy worker in Texas, who has since recovered, was confirmed positive. Ongoing surveillance of emergency department visits and flu testing results in regions with bird flu have not identified any unusual or concerning patterns, the CDC’s principal deputy director, Nirav Shah, said Wednesday. The risk to the public from bird flu remains low.

For dairy farmers, the potential impact on their business is top of mind.

“Lots of farms aren’t raising their hands to be tested because they don’t want to be known as having an infected herd,” said Keith Poulsen, director of the veterinary diagnostic lab at the University of Wisconsin-Madison.

Jamie Jonker, chief science officer for the National Milk Producers Federation, described as appropriate the USDA announcement on testing and interstate movement. But milk producers are waiting for the USDA’s detailed guidance to know how many tests may need to be performed on milk cows, estimated to number about 8 million, Jonker said.

The testing mandate could help overcome reluctance from some milk producers to allow testing in their herds, the USDA’s Mike Watson said Wednesday. The cost of mandatory testing would be reimbursed by the agency.

A wide swath of federal agencies are mobilizing in the event the highly pathogenic virus evolves.

At highest risk are farmworkers, who, like many in the agriculture sector, are undocumented or do not wish to interact with the government, Shah said.

In an emergency call three weeks ago with state health and lab officials, Shah laid out a detailed list of operational questions state officials needed to answer to prepare for potential exposures in people.

“What nurse and what epidemiologist have you trained up to do this? Do you have the [nasal] swabs ready? Do they know how to approach that conversation in a culturally competent and linguistically competent manner? … Is the lab ready to go?”

Dan Diamond and Fenit Nirappil contributed to this report.