Pandemic Center

The U.S. Department of Agriculture fired several personnel responsible for working to stop the spread of the H5N1 avian flu over the weekend. The agency is now trying to find and rehire those workers. The bird flu has affected more than 160 million birds nationally since 2022, contributing to rocketing egg prices and the endangerment of farm workers.
The U.S. Department of Agriculture is working to rehire employees it fired over the weekend, many of whom were part of the federal government’s efforts to stop the spread of the virulent H5N1 avian flu that has killed millions of livestock and contributed to sky-high egg prices.

“Although several positions supporting [bird flu efforts] were notified of their terminations over the weekend, we are working to swiftly rectify the situation and rescind those letters,” a USDA spokesperson told Fortune in a statement. “USDA’s Food Safety and Inspection Service frontline positions are considered public safety positions, and we are continuing to hire the workforce necessary to ensure the safety and adequate supply of food to fulfill our statutory mission.”

The spokesperson said job categories within the USDA, such as veterinarians and emergency response personnel, were exempted from the sackings.

The H5N1 avian flu has wrought havoc on U.S. agriculture. More than 162 million birds and nearly 1,000 dairy cow herds in the U.S. have been affected by the avian flu since 2022, according to the Centers for Disease Control and Prevention and USDA, which has contributed to about 20 million deaths of egg-laying hens in the last quarter of 2024 alone.

About 70 people in the U.S. have contracted the disease since the 2022 outbreak; the CDC reported the first human death from H5N1 last month.

The elimination of key USDA positions is part of an effort by President Donald Trump and the Department of Government Efficiency to cull thousands of government positions in an effort to overhaul bureaucracy and curb federal spending. Some USDA employees, including those from the National Animal Health Laboratory Network program office overseeing the response to animal-borne disease outbreaks, were notified Friday their jobs would be eliminated, Politico reported.

“They’re the front line of surveillance for the entire outbreak,” Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory, told Politico. “They’re already underwater and they are constantly short-staffed, so if you take all the probationary staff out, you’ll take out the capacity to do the work.”

Consequences of federal workplace uncertainty
The USDA is the country’s first line of defense in understanding and combating the avian flu because of its access to the farms battling the brunt of the virus’s consequences, according to Jennifer Nuzzo, director of the pandemic center at the Brown University School of Public Health. The agency’s surveillance efforts of farms, such as bulk testing raw milk for disease, is the primary means of gathering information about the virus and its spread.

Beyond staff shortages siphoning resources from that work, the anxiety around sweeping personnel changes alone may prevent USDA employees from focusing on constraining the virus.

“With this changing policy environment and the uncertainty about all of the personnel, government worker personnel issues, agencies are spending a lot of their time just trying to navigate that highly chaotic and uncertain situation,” Nuzzo told Fortune, “which I believe is interfering with their abilities to fulfill their statutory missions.”

Besides firing thousands of public health workers, the Trump administration has also hampered response to the bird flu outbreak, with the CDC and USDA unable to hold congressional briefings, meet with state officials, or receive internal reports, according to multiple reports.

The White House did not immediately respond to Fortune’s request for comment.

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The Trump administration’s new approach to communicating health and medical data has left a hazy picture of the country’s fight against bird flu and has complicated the relationship between the federal health bureaucracy and state agencies.

While some state health officials told NOTUS they’ve continued to get what they need from the Centers for Disease Control and Prevention, other officials and outside experts say they’re worried about what they’re not being told and how that could be hampering the urgent push against H5N1.

But at least some of the dysfunction of the federal health agencies has trickled down to the states that have had human infections, say some pandemic experts and health officials — making responding to the ongoing H5N1 outbreak that much harder.

Washington state epidemiologist Scott Lindquist said it’s been difficult for state health officials to understand the scope of the outbreak. “Normally, we would be having pretty regular updates, but I’ve seen one health alert come out last week,” he said on Feb. 13.

Alabama medical officer Burnestine Taylor said that they have had “absolutely no communications” from the federal health agencies recently.

“We’re basically just kind of continuing with the groundwork that was laid before the halt in communication,” Taylor said. “We’re carrying on and doing what we had planned to do, but we no longer have direct communication with them.”

But other states said that their work coordinating public health operations with the CDC hasn’t been interrupted in any meaningful way.

“We appear to be working very seamlessly, particularly even through this new administration change,” said Jae Williams, a spokesperson for the Florida Department of Health. “They’re still getting things situated up in D.C., but it hasn’t slowed down our operations at all.”

H5N1, also known as avian influenza or bird flu, has been circulating in U.S. poultry and cattle since early last year. Upwards of 60 human infections occurred in the U.S. and Canada last fall. Cases occurred mostly in workers on dairy farms — though several people were infected who had no known contact with livestock or birds. One person with underlying health conditions died in Louisiana late last year.

The scope of the outbreak in humans has continued to expand in 2025: Ohio announced its first human H5N1 case last week, joining Washington, Oregon, California, Nevada, Colorado, Texas, Louisiana, Iowa, Missouri, Wisconsin and Michigan as states that have seen infections in humans. While state agriculture departments and the U.S. Department of Agriculture have taken the lead in responding to the H5N1 outbreak in animals, the CDC has played a critical role in tracking human cases and issuing guidance to researchers and epidemiologists tracking the outbreak.

All that came to a thudding halt after Trump issued an executive order freezing communication from the federal health agencies. While some communication appears to have been restored, scientists say what they’ve heard from the CDC still seems to be limited.

“It’s really alarming, the lack of communication about H5N1,” said Jennifer Nuzzo, director of the Pandemic Center at Brown University. “I have to assume that we haven’t heard big developments because big developments haven’t happened, but we also haven’t heard information about what’s ongoing to make sure big developments aren’t happening.”

A spokesperson for the Massachusetts Department of Public Health said in an email that they have seen very limited outreach from the CDC since the change in administration. They added that the CDC held only one national call, which covered multiple public health topics and was too large to permit useful question and answer periods. Communications between the U.S. Department of Agriculture and state agriculture agencies have apparently been less affected, said the spokesperson.

Reports that the CDC withheld multiple issues of a key weekly report for the first time since the 1960s — and that the withheld reports were about H5N1 — is a sign that things are deeply unwell at the CDC, said Nuzzo.

“It’s really puzzling to me why we’re not releasing information that is essential to understand what risk this virus poses to people and how best to protect them,” Nuzzo said.

KFF Health News recently found that a CDC report on record-high seasonal flu levels had been delayed for release, and that the Advisory Committee to the Director of the CDC wrote to acting CDC Director Susan Monarez asking her to explain the delay.

But some state health officials said that the pause in communications either wasn’t noticeable or didn’t impact their day-to-day activities at all.

“There has been no substantial change in communication with the Federal government,” a spokesperson for the New York health commissioner, Danielle De Souza, said in an email. And a spokesperson for the Nevada Department of Health and Human Services said that “the CDC has been a responsive partner and has been in communication and collaboration with DHHS throughout the response.”

A spokesperson for the South Carolina Department of Public Health said in an email that communications about H5N1 occur between state and federal health officials at least weekly “during regularly scheduled calls, but also on an as-needed basis via calls or emails.” And Oklahoma State Epidemiologist Jolianne Stone said that while they often rely on other states or other public health partners for guidance on outbreaks like H5N1, they have had “communication with CDC technical support and with CDC if needed.”

State health departments are responsible for a broad range of disease response efforts for outbreaks like H5N1. These can range from giving personal protective equipment to farms, to outreach and education for high-risk populations or testing exposed individuals for infections and monitoring them for symptoms. States often make decisions on how best to respond to outbreaks based on the guidance and data the CDC issues.

Lindquist said that while he has still been able to get in touch with individual subject matter experts at the CDC, he’s concerned that the data consolidation and guidance that the CDC does for the states has been impacted by the communications freeze. The last update to the CDC Health Alert Network related to H5N1 was released on Jan. 16 and issued guidance for testing some influenza patients for H5N1.

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As avian flu drives egg prices to record levels and increasingly poses a risk to humans, moves by the White House to cut spending and restrict communications have hobbled public health officials’ response, with the new administration yet to outline a clear strategy on how it plans to stem the spread of the virus.

State and local public health officials have gone weeks without regular updates on avian flu from the Centers for Disease Control and Prevention after President Donald Trump froze nearly all external communications from the agency, said a person familiar with the situation. It wasn’t until this week that some of those communications began to resume, the person said.

Widespread funding cuts across the government and new restrictions on funding for National Institutes of Health grants have also created uncertainty among infectious disease researchers and local health officials, who are unsure about what resources they will have to work with going forward. Meanwhile, cuts to the U.S. Agency for International Development have limited monitoring of the virus overseas.

“When you add that uncertainty, it plays into what health departments can do when their entire funding situation is at risk,” said Adriane Casalotti, chief of government and public affairs for the National Association of County and City Health Officials. “It makes it even harder to do more when you don’t think you’ll have the resources or they might get pulled out from under you.”

At the same time, key positions in the Trump administration central to responding to the threat of a pandemic have remained unfilled. And the secretaries running the Health and Human Services and Agriculture departments weren’t confirmed until this week, though bird flu was one of the first items on Agriculture Secretary Brooke Rollins' agenda after her confirmation.

The disruptions come at a potentially perilous time. The virus has been decimating poultry flocks, causing egg prices to more than double. It has been showing signs it can evolve to more easily thrive in a variety of species, including a new strain detected among dairy cattle this month. While there are no indications the virus can be transmitted among humans, at least 68 people in the U.S. have contracted avian flu and one person has died, according to the CDC. Researchers worry that the more the virus replicates, the more opportunities it will have to develop a mutation that would enable it to spread easily from human to human.

“This is getting more and more dangerous and urgent, and the scientific community is setting off alarm flares,” said Stephen Morrison, who directs the global health policy center at the Center for Strategic and International Studies. “But are they translating into the government moving at a faster pace or with a different resolve? No. Instead, we’re in a period of confused transition that’s been made worse by the disruptions in government function and the normal slowness of getting the new team in.”

The White House didn’t respond to a request for comment on its strategy for addressing avian flu and what additional steps it planned to take to address the spread of the virus.

Rollins, who was confirmed by the Senate Thursday, told reporters that she had a briefing in the Oval Office Thursday night and would be announcing more on the department’s plan to address egg prices “in the coming days.”

“We are looking at every possible scenario to ensure that we are doing everything we can in a safe, secure manner, but also to ensure that Americans have the food that they need,” Rollins said when asked about the price of eggs. “And as a mom of four teenagers, actually, I fully understand and feel the pain of the cost of these eggs.”

White House National Economic Council Director Kevin Hassett said in an interview on MSNBC Thursday that the Trump administration would soon have a strategy now that Rollins has been confirmed.

“It turns out, President Biden’s team didn’t have an avian flu strategy, and now we’re about to have one, as soon as Brooke Rollins is at the Department of Agriculture,” said Hassett.

In a statement on egg prices earlier this week, the White House said Rollins would take “bold, decisive action to address the crisis” by refocusing the agency tasked with stopping the spread of the virus among animals “on its core mission: protecting the health of the United States’ plants, animals, and natural resources while simultaneously lowering costs.”

So far, though, public health officials say the White House has created more confusion than clarity.

In West Virginia, Michael Kilkenny, head of the Huntington Health Department, said he hasn’t been getting regular updates from the CDC for the past several weeks.

“We just don’t know what’s happening right now. We don’t know if this is expanding into our area if we aren’t getting that communication from the CDC,” said Kilkenny. “In more rural areas, there are small health departments that, without the information they need coming from the CDC, they’re not going to be able to inform their small-flock farmers, poultry farmers or higher-risk agricultural workers that depend on the local health department for information or services.”

The prospect of potential federal funding cuts have also caused his and other health departments he works with to begin contingency planning and put hiring and new projects on hold.

“We are holding on hiring and we are holding on planning while we are waiting to see that there is clear evidence that things are going to be funded before we can spend our work time planning or even submitting for a project,” said Kilkenny. “That is how this disrupts us.”

Along with limiting CDC communications with local health officials, the World Health Organization has also been receiving limited information on the spread of avian flu in the U.S. since Trump signed an executive order to withdraw from the global health organization, WHO director-general Tedros Adhanom Ghebreyesus said during a Feb. 12 press conference.

The “near-total communication freeze” at public health agencies “is deeply unprecedented, and that alone scares me more than anything else,” said Jennifer Nuzzo, director of the pandemic center at the Brown University School of Public Health.

Nearly a month in, Trump has yet to name an official to head the White House Office of Pandemic Preparedness and Response Policy, which was created in 2022 by Congress to coordinate pandemic response across agencies. During the campaign, Trump said he would likely get rid of the office and criticized President Joe Biden’s efforts to prepare for another pandemic.

“He wants to spend a lot of money on something that you don’t know if it’s gonna be 100 years or 50 years or 25 years,” Trump said of Biden in a July interview with Time magazine. “And it’s just a way of giving out pork.”

“It doesn’t mean that we’re not watching out for it all the time,” Trump said. “But it’s very hard to predict what’s coming because there are a lot of variations of these pandemics.”

Trump’s key Cabinet officials who will be overseeing the federal response have given little insight into their strategy.

Rollins said during her Senate confirmation hearing last month that one of her top four priorities would be to put a team in place to stem the spread of avian flu, though she didn’t say what changes she would like to see the Agriculture Department make.

“There is a lot that I have to learn on this, and if confirmed, this will be, as I mentioned in my opening statement, one of the very top priorities,” Rollins said when asked about her response to avian flu. “We are hyperfocused on finding the team right now. I’m sure they’re already working. I have, obviously, respected the process and not gotten too involved. I know that the current team and the future team will be working hand in hand to do everything we can on animal disease.”

Health and Human Services Secretary Robert F. Kennedy Jr., who was confirmed by the Senate on Thursday, said during his confirmation hearing that he would focus more on tackling chronic disease, like heart disease and diabetes, and less on infectious diseases. When asked about devoting resources to avian flu during his confirmation hearing, Kennedy said he “intends to devote the appropriate resources to preventing pandemics. That’s essential for my job.”

Previously, Kennedy has said the currently available vaccines for avian flu that the U.S. has stockpiled may be dangerous and ineffective. Researchers are working on developing a new generation of avian flu vaccines based on the same mRNA technology used to develop the Covid vaccines, which Kennedy called the “the deadliest vaccine ever made,” though studies have shown it to be safe.

Kennedy has also been a proponent of drinking raw milk, which can put people at risk of foodborne illness, including avian flu. The CDC has warned that it might be possible to contract bird flu from drinking raw milk and urged Americans to drink only pasteurized milk.

Agriculture industry officials and infectious disease researchers have been calling on the federal government to significantly ramp up its response with greatly expanded testing, funding for research to better understand the virus and develop new treatments, and more assistance for dairy farmers to encourage them to test their cattle.

The United Egg Producers, an advocacy group for the egg industry, is urging the federal government and Congress to devote more resources to researching how the virus is spreading and evolving and to develop more effective and widespread vaccinations for animals. The industry group has also been calling for more rules and enforcement around the testing and movement of animals, and additional funding for local laboratories to provide quick and accurate test results.

“Our industry needs more from our state and federal government animal health partners — and we need it fast,” the United Egg Producers said in a statement.

The organization says its industry has lost more than 100 million egg-laying hens since 2022, including more than 29 million over the past four months. Once a flock of birds is infected with the highly pathogenic strain of the avian flu, the virus quickly spreads and is fatal in the vast majority of birds. When a flock becomes infected, farmers and veterinarians are supposed to notify the USDA, which will kill the entire flock and decontaminate the facilities. The federal government reimburses the farmers for the live birds that are culled in the process.

Public health researchers have said the Biden administration didn’t react quickly enough to stop the spread of the virus among dairy cattle after it was first detected in herds in March. It wasn’t until December that the Agriculture Department rolled out a national milk testing program, and three of the country’s top milk-producing states still aren’t a part of that federal surveillance effort.

The Trump administration will have to work with officials in states that still aren’t regularly testing their milk to try to get them on board, said Morrison. Texas’ state agriculture commissioner, Sid Miller, told NBC News that surveillance milk testing was unnecessary in Texas since there weren’t any active cases of bird flu in the state’s commercial cattle or poultry.

“From April until the end of the Biden administration, the response was slow and sluggish,” said Morrison. “We are still not testing animals and humans at the level that is needed, we still don’t have a coherent strategy and a system of accountability, and we still don’t have in place the kind of compensation mechanisms needed for those dairy farmers who suffer losses because of infections in their herds.”

Researchers worry the U.S. is running out of time to strengthen its response.

“If we don’t act now, we’re only giving the virus more opportunity to continue to adapt and potentially evolve into something more dangerous in a human population,” said Erin Sorrell, a senior scholar at the Johns Hopkins Center for Health Security. “Now is the time to act.”


Shannon Pettypiece

Sonya Stokes, an emergency room physician in the San Francisco Bay Area, braces herself for a daily deluge of patients sick with coughs, soreness, fevers, vomiting, and other flu-like symptoms.

She’s desperate for information, but the Centers for Disease Control and Prevention, a critical source of urgent analyses of the flu and other public health threats, has gone quiet in the weeks since President Donald Trump took office.

“Without more information, we are blind,” she said.

Flu has been brutal this season. The CDC estimates at least 24 million illnesses, 310,000 hospitalizations, and 13,000 deaths from the flu since the start of October. At the same time, the bird flu outbreak continues to infect cattle and farmworkers. But CDC analyses that would inform people about these situations are delayed, and the CDC has cut off communication with doctors, researchers, and the World Health Organization, say doctors and public health experts.

“CDC right now is not reporting influenza data through the WHO global platforms, FluNet [and] FluID, that they’ve been providing information [on] for many, many years,” Maria Van Kerkhove, interim director of epidemic and pandemic preparedness at the WHO, said at a Feb. 12 press briefing.

“We are communicating with them,” she added, “but we haven’t heard anything back.”

On his first day in office, President Donald Trump announced the U.S. would withdraw from the WHO.

A critical analysis of the seasonal flu selected for distribution through the CDC’s Health Alert Network has stalled, according to people close to the CDC. They asked not to be identified because of fears of retaliation. The network, abbreviated as HAN, is the CDC’s main method of sharing urgent public health information with health officials, doctors, and, sometimes, the public.

A chart from that analysis, reviewed by KFF Health News, suggests that flu may be at a record high. About 7.7% of patients who visited clinics and hospitals without being admitted had flu-like symptoms in early February, a ratio higher than in four other flu seasons depicted in the graph. That includes 2003-04, when an atypical strain of flu fueled a particularly treacherous season that killed at least 153 children.

Without a complete analysis, however, it’s unclear whether this tidal wave of sickness foreshadows a spike in hospitalizations and deaths that hospitals, pharmacies, and schools must prepare for. Specifically, other data could relay how many of the flu-like illnesses are caused by flu viruses — or which flu strain is infecting people. A deeper report might also reveal whether the flu is more severe or contagious than usual.

“I need to know if we are dealing with a more virulent strain or a coinfection with another virus that is making my patients sicker, and what to look for so that I know if my patients are in danger,” Stokes said. “Delays in data create dangerous situations on the front line.”

Although the CDC’s flu dashboard shows a surge of influenza, it doesn’t include all data needed to interpret the situation. Nor does it offer the tailored advice found in HAN alerts that tells health care workers how to protect patients and the public. In 2023, for example, a report urged clinics to test patients with respiratory symptoms rather than assume cases are the flu, since other viruses were causing similar issues that year.

“This is incredibly disturbing,” said Rachel Hardeman, a member of the Advisory Committee to the Director of the CDC. On Feb. 10, Hardeman and other committee members wrote to acting CDC Director Susan Monarez asking the agency to explain missing data, delayed studies, and potentially severe staff cuts. “The CDC is vital to our nation’s security,” the letter said.

Several studies have also been delayed or remain missing from the CDC’s preeminent scientific publication, the Morbidity and Mortality Weekly Report. Anne Schuchat, a former principal deputy director at the CDC, said she would be concerned if there was political oversight of scientific material: “Suppressing information is potentially confusing, possibly dangerous, and it can backfire.”

CDC spokesperson Melissa Dibble declined to comment on delayed or missing analyses. “It is not unexpected to see flu activity elevated and increasing at this time of the year,” she said.

A draft of one unpublished study, reviewed by KFF Health News, that has been withheld from the MMWR for three weeks describes how a milk hauler and a dairy worker in Michigan may have spread bird flu to their pet cats. The indoor cats became severely sick and died. Although the workers weren’t tested, the study says that one of them had irritated eyes before the cat fell ill — a common bird flu symptom. That person told researchers that the pet “would roll in their work clothes.”

After one cat became sick, the investigation reports, an adolescent in the household developed a cough. But the report says this young person tested negative for the flu, and positive for a cold-causing virus.

Corresponding CDC documents summarizing the cat study and another as-yet unpublished bird flu analysis said the reports were scheduled to be published Jan. 23. These were reviewed by KFF Health News. The briefing on cats advises dairy farmworkers to “remove clothing and footwear, and rinse off any animal biproduct residue before entering the household to protect others in the household, including potentially indoor-only cats.”

The second summary refers to “the most comprehensive” analysis of bird flu virus detected in wastewater in the United States.

Jennifer Nuzzo, director of the Pandemic Center at Brown University, said delays of bird flu reports are upsetting because they’re needed to inform the public about a worsening situation with many unknown elements. Citing “insufficient data” and “high uncertainty,” the United Kingdom raised its assessment of the risk posed by the U.S. outbreak on dairies.

“Missing and delayed data causes uncertainty,” Nuzzo said. “It also potentially makes us react in ways that are counterproductive.”

Another bird flu study slated for January publication showed up in the MMWR on Feb. 13, three weeks after it was expected. It revealed that three cattle veterinarians had been unknowingly infected last year, based on the discovery of antibodies against the bird flu virus in their blood. One of the veterinarians worked in Georgia and South Carolina, states that haven’t reported outbreaks on dairy farms.

The study provides further evidence that the United States is not adequately detecting cases in cows and people. Nuzzo said it also highlights how data can supply reassuring news. Only three of 150 cattle veterinarians had signs of prior infections, suggesting that the virus doesn’t easily spread from the animals into people. More than 40 dairy workers have been infected, but they generally have had more sustained contact with sick cattle and their virus-laden milk than veterinarians.

Instead, recently released reports have been about wildfires in California and Hawaii.

“Interesting but not urgent,” Nuzzo said, considering the acute fire emergencies have ended. The bird flu outbreak, she said, is an ongoing “urgent health threat for which we need up-to-the-minute information to know how to protect people.”

“The American public is at greater risk when we don’t have information on a timely basis,” Schuchat said.

This week, a federal judge ordered the CDC and other health agencies to “restore” datasets and websites that the organization Doctors for America had identified in a lawsuit as having been altered. Further, the judge ordered the agencies to “identify any other resources that DFA members rely on to provide medical care” and restore them by Feb. 14.

In their letter, CDC advisory committee members requested an investigation into missing data and delayed reports. Hardeman, an adviser who is a health policy expert at the University of Minnesota, said the group didn’t know why data and scientific findings were being withheld or removed. Still, she added, “I hold accountable the acting director of the CDC, the head of HHS, and the White House.”

Hardeman said the Trump administration has the power to disband the advisory committee. She said the group expects that to happen but proceeded with its demands regardless.

“We want to safeguard the rigor of the work at the CDC because we care deeply about public health,” she said. “We aren’t here to be silent.”

Amy Maxmen: amaxmen@kff.org

CNN
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Blood testing of large-animal veterinarians suggests that H5N1 bird flu has spread more widely than US surveillance of the virus is capturing, according to a new study by federal and state disease detectives.

The study comes as Ohio announced its first human case of H5N1 in a poultry worker who was hospitalized with respiratory symptoms but has since recovered.

The new study of vets found that three of the 150 who signed up to be tested – or 2% – had antibodies against bird flu in their blood. Antibodies indicate that the vets were infected with bird flu, although they didn’t have symptoms.

It is one of three studies on bird flu that were delayed after the Trump administration issued a pause on outside communications from federal health agencies last month.

The study on blood testing of vets who treat cows was released Thursday in the Morbidity and Mortality Weekly Report, which is published by the US Centers for Disease Control and Prevention.

The other studies, which still have not been released, reportedly detail transmission between cats infected with bird flu and people in the same household, and discuss H5N1 detections in wastewater.

Blood tests in veterinarians
For the research, called a seroprevalence study because it looks for evidence of infections in the blood to try to determine a population’s exposure to disease, researchers from the CDC and the Ohio Department of Health went to the annual meeting of the American Association of Bovine Practitioners, which was held in September in Columbus.

Before the meeting, the CDC emailed members to ask whether they’d like to participate. It enrolled 150 veterinarians from 46 states and Canada who had their blood drawn at the conference. Just over half were from states known to have positive dairy herds, and 1 in 4 said they’d worked with infected cattle.

Three vets’ blood tests came back positive for antibodies to the H5N1 virus, even though none of them had experienced any memorable symptoms or worked with cows that had tested positive for H5N1. One vet who had antibodies had worked with infected poultry, however, according to the study.

One veterinarian who tested positive said they’d treated cattle in Georgia and South Carolina, two states with no reported infections in cows.

The report’s authors write that their findings suggest there may be H5N1 infections in cows in states that haven’t reported any, and they highlight the need for faster and more comprehensive testing of animals and milk to identify infected herds.

Dr. Jennifer Nuzzo, who directs the Pandemic Center at Brown University, said the study had good news and bad news.

The bad news, she said, is that bird flu is spreading where we don’t have eyes on it.

“I think the bottom line here is that there are vets who may have been infected in states that hadn’t reported outbreaks, which is bad,” Nuzzo said. “It speaks to the need to improve our surveillance so that we can better detect when outbreaks are occurring on farm so we can protect people.”

The good news is that the researchers didn’t see evidence of a large number of under-the-radar infections.

“We’re not missing some huge submerged iceberg of mild infections that would possibly make us think that this virus could be much milder than what it has historically been,” Nuzzo said.

Other experts said the study spoke to some of the challenges veterinarians face in protecting themselves from the virus.

“This report tells us is that this virus can infect and present without symptoms in animals and that enough virus is shed either directly from animal to veterinarian or via touching surfaces to infect the vet,” said Dr. Erin Sorrell, a senior scholar at the Johns Hopkins Center for Health Security. Nuzzo and Sorrell did not work on the new study.

Bird flu infections in humans remain rare
There is no evidence that H5N1 is spreading from person to person. The CDC says the risk to the public remains low, although people who work on farms and with infected animals, or who have backyard poultry flocks, are at higher risk of an H5N1 infection.

Since March 2024, there have been 68 confirmed H5N1 infections in people in the US. All but three have had known exposures to animals.

Two of those cases have been severe, including an older person in Louisiana who died last year.

The most recent serious infection was a farm worker in Ohio who had contact with infected birds. Ohio announced its first bird flu case in a human on Wednesday.

That person was hospitalized with respiratory symptoms but has since recovered, according to a health official familiar with the details of the case who was not authorized to speak to the media.

The subtype of the virus has not been confirmed, but it is probably the newer strain, D1.1, the official said.

A new study published by the U.S. Centers for Disease Control and Prevention shows that the H5N1 bird flu virus is probably circulating undetected in livestock in many parts of the country and may be infecting unaware veterinarians.

In the health agency’s Morbidity and Mortality Weekly Report, a group of researchers from the CDC, the Ohio Department of Health and the American Assn. of Bovine Practitioners, reported the results of an analysis they conducted on 150 bovine, or cow, veterinarians from 46 states and Canada.

They found that three of them had antibodies for the H5N1 bird flu virus in their blood. However, none of the infected vets recalled having any symptoms — including conjunctivitis, or pink eye, the most commonly reported symptom in human cases.

The three vets also reported to investigators that they had not worked with cattle or poultry known to be infected with the virus. In one case, a vet reported having practiced only in Georgia (on dairy cows) and South Carolina (on poultry) — two states that have not reported H5N1 infections in dairy cows.

Seema Lakdawala, a microbiologist at Emory University in Atlanta — who was not involved in the research — said she was surprised that only 2% of the veterinarians surveyed tested positive for the antibodies, considering another CDC study showed that 17% of dairy workers sampled had been infected. But she said she was even more surprised that none of them had known they were infected or that they had worked with infected animals.

“These surprising results indicate that serum surveillance studies are important to inform risk of infections that are going undiagnosed,” she said. “Veterinarians are on the front line of the outbreak, and increased biosafety practices like respiratory and eye protection should reduce their exposure risk.”

Jennifer Nuzzo, director of the Pandemic Center at Brown University, described the study as a “good and bad news story.”

“On one hand, we see concerning evidence that there may be more H5N1 outbreaks on farms than are being reported,” she said. “On the other hand, I’m reassured that there isn’t evidence that infections among vets have been widespread. This means there’s more work that can and should be done to prevent the virus from spreading to more farms and sickening workers.”

The analysis was conducted in September 2024. At that time, there had been only four human cases reported, and the infection was believed to be restricted to dairy cattle in 14 states. Since then, 68 people have been infected — 40 working with infected dairy cows — and the virus is reported have infected herds in 16 states.

John Korslund, a retired U.S. Department of Agriculture scientist, said in an email that finding H5N1 antibodies in the blood of veterinarians was an interesting “but very imprecise way to measure state cattle incidence.” But it underscored “that humans ARE susceptible to subclinical infections and possible reassortment risks, which we already knew, I guess.”

Reassortment occurs when a person or animal is infected with more than one influenza virus, allowing the two to mingle and exchange “hardware,” potentially creating a new, more virulent strain.

More important, he said, the D1.1 version of the strain — which has been detected in Nevada dairy cattle and one person living in the state — is “changing the landscape. ... [P]eople may be more more susceptible (or not) with a greater potential for severeness (or not).”

“I’m confident that we’ll find it in other states. Its behavior and transmissibility within and between cattle herds is still pretty much a black box,” he said.

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