(Bloomberg) -- Its spreading rapidly among cows. Its also infecting skunks, mountain lions and red foxes.
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Yet as the highly contagious avian flu affects mammals across the US, just one human case has been reported so far.
But thats probably only because there is extremely limited testing of people underway to detect it. State governments and farm owners have kept Centers for Disease Control and Prevention teams from conducting on-the-ground investigations that would offer a fuller picture of the prevalence of the virus in humans.
That threatens to impair federal officials response to an outbreak that many experts view as the biggest test for pandemic readiness systems since Covid-19. The recent patient is recovering after experiencing eye redness as their sole symptom. However, avian flu typically kills half the people known to have been infected, hinting at the danger it poses if it were to spread widely.
The CDC does not have authorization to carry out on-the-ground investigations without an invitation, and the states that have confirmed infected cattle say they have not made such an overture to the agency.
Private dairy farms would also have to welcome the CDC investigators, a fraught proposition in an industry heavily reliant on immigrant workers who are often leery of interacting with government officials and worried about losing income if they test positive. Farms may also be reluctant to scour for infected cows, out of concern that might have downsides for their low-profit margin businesses.
The CDC is not able to go in and do the type of testing and investigative work they need to do, Abraar Karan, an infectious disease researcher at Stanford University, said. Thats a huge problem and its a blatant issue.
The CDC says the current risk to the general public from bird flu is low, because its not known to transmit efficiently from person to person. But each infection in a cow or human provides an opportunity for the virus to mutate and become better adapted to mammalian respiratory cells.
Key to understanding that risk and preventing the emergence of a deadly pandemic is the ability to detect the infection and track molecular changes in the virus.
Were playing with fire, said Sam Scarpino, a professor at Northeastern University, who helped lead pathogen surveillance at the Rockefeller Foundation during the coronavirus pandemic. Were really not doing the surveillance to say that its not here.
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On-The-Ground Testing
CDC Director Mandy Cohen said her agency is prepared to conduct on-the-ground bird flu testing and other forms of surveillance.
We are ready to deploy, Cohen said in an interview Monday. We have been for weeks. Those on standby at the CDC include multilingual and multidisciplinary epidemiological teams.
Yet the nine states with infected cattle Texas, New Mexico, Michigan, Kansas, Idaho, Colorado, North Carolina, Ohio and South Dakota said in statements they have not invited the CDC.
In New Mexico and Texas, the only two states that have reported conducting testing of their own, the scope of that work has been limited. New Mexico tested three people for avian flu, a spokesperson said in an email.
The Texas Department of State Health Services tested about 20 people, with one positive case in a dairy farm worker. The worker showed signs of conjunctivitis with red, swollen eyes and returned to work the day after testing. A spokesperson for the department said it hasnt invited the CDC because we have not found any dairy farms interested in participating in an epidemiological field study.
Since March, more than 30 people have been tested for novel influenza A, the broad category of flu that includes H5N1, and over 220 have been monitored for symptoms, many of whom are being asked to self-report signs of disease, according to the CDC.
The CDC is monitoring multiple flu indicators, and Cohen notes that data from emergency rooms and commercial laboratories across the US isnt currently showing concerning patterns.
The good news is were not seeing anything unusual, Cohen said, such as a spike in doctors ordering flu tests.
Yet she also stressed the need to continue to work with agriculture partners especially given the novel nature of how this strain of bird flu is spreading.
There is a very robust way in which weve worked with our poultry farmers, but this is new in cattle, Cohen said.
Huge Problem
The FDA found traces of the H5N1 virus in 1 in 5 retail milk samples. Although pasteurization has been shown to render the pathogen harmless, that incidence shows it has spread widely among cows. In the US, some 36 dairy herds are known to have been affected.
The USDA recently said its scouring for manufacturers who are interested in making a safe and effective vaccine for use in cattle targeting the virus.
The people most likely to be infected dairy farm workers who have their hands on cows regularly arent necessarily going to doctors for treatment, community health workers say.
Wastewater testing in Texas found H5N1 traces, which could be attributed to humans or animals with the virus. Of hundreds of sites looked at weekly by a research group, a trio were tested for genetic markers of H5N1, and all three were confirmed to have it. Researchers wrote that cows milk entering sewage systems is a likely explanation for those findings.
Weve almost certainly missed human cases, Scarpino said, referencing the Texas wastewater findings. The real question we need to answer is: Are there thousands of flu cases we missed, or a handful?
Worker Reluctance
Even if the CDC were to gain authorization from states and farms to perform onsite testing, it would face additional challenge: Workers would have to agree to participate, and many of them would likely be hesitant to do so.
Fear of job loss, language barriers, transportation costs and distrust in public health systems are all factors that might deter migrants from consenting to test, said Bethany Alcauter, director of research at the National Center for Farmworker Health. She said the situation reminds her of the early days of the coronavirus pandemic, when workers were reluctant to test and the illness wasnt well understood.
Lus Chavez, rural outreach director at Family Support Services in Amarillo, Texas, said she spoke with dairy workers in late February with flu-like symptoms including congestion, but they tested negative for flu and Covid. The farm workers, she said, were convinced it was a new strain of Covid that wasnt showing up on tests.
Chavez said she has been contacted by the Texas health department to advertise that it can provide voluntary tests, but workers are reluctant to do so out of fear of retaliation for raising concerns or worries about losing pay.
Even if workers elect to test, there is no requirement to reveal where they work, another challenge for authorities trying to track and contain the virus.
The CDC is engaged in discussions with multiple states about setting up field investigations to answer questions about the ongoing outbreak, including by examining flu antibodies in blood samples from farm workers in order to see if any of them had been previously infected. The CDC would help establish protocols for studies that would allow data to be standardized across states. Such an effort could similarly face hesitation from farms and staff.
Its not just a dearth of bird-flu testing that concerns public health experts. A lack of funding and research, some say, has also left the US flatfooted if a wider outbreak of bird flu or any other deadly virus takes hold.
Were not going to be ready, Katrine Wallace, epidemiologist at the University of Illinois, said. Were not even dealing with whats right in front of us.
--With assistance from Madison Muller.
(Updates with USDA announcement, adds details about wastewater treatment study)
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The bird flu virus sweeping across dairy farms in multiple states has acquired dozens of new mutations, including some that may make it more adept at spreading between species and less susceptible to antiviral drugs, according to a new study.
None of the mutations is a cause for alarm on its own. But they underscore the possibility that as the outbreak continues, the virus may evolve in ways that would allow it to spread easily between people, experts said.
Flu mutates all the time its what, sort of, flu does, said Richard Webby, an influenza expert at St. Jude Childrens Research Hospital, who was not involved in the work.
The real key would be if we start to see some of these mutations getting more prevalent, Dr. Webby said. That would raise the risk level.
The virus, called H5N1, has infected cows in at least 36 herds in nine states, raising fears that milk could be infectious concerns now largely put to rest and highlighting the risk that many viruses might jump across species on crowded farms.
The study was posted online on Wednesday and has not been peer reviewed. It is among the first to provide details of a Department of Agriculture investigation that has been mostly opaque until now, frustrating experts outside the government.
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WASHINGTON The commissioner of the U.S. Food and Drug Administration said at a congressional hearing Wednesday the agency is preparing for the possibility the strain of avian influenza affecting dairy cattle could jump to humans, though he cautioned the probability is low.
Robert Califf told senators on the panel in charge of his agencys funding that top officials from the FDA, Agriculture Department and Centers for Disease Control and Prevention are speaking daily to keep a handle on the situation. He also stressed that pasteurized milk is safe.
This virus, like all viruses, is mutating, Califf said. We need to continue to prepare for the possibility that it might jump to humans.
Califf told senators that the real worry is that it will jump to the human lungs where, when that has happened in other parts of the world for brief outbreaks, the mortality rate has been 25%.
That would be about 10 times worse than the death rate from COVID-19, he said.
Califf stressed the possibility is low and the CDC continues to maintain its assessment that the current public health risk is low.
The H5N1 bird flu strain has had an impact on 36 dairy herds in Colorado, Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio, South Dakota and Texas, according to the CDC.
Two cases have been reported in people one who had exposure to dairy cows in Texas that were presumed to be infected and one in Colorado involved in the culling (depopulating) of poultry with presumptive H5N1 bird flu. Both cases were reported in April, according to the CDC.
The Texas case reported eye redness (consistent with conjunctivitis), as their only symptom while the Colorado case reported fatigue for a few days as their only symptom and has since recovered, according to the CDC.
Califf told the Senate Agriculture Appropriations Subcommittee during the hearing the Agriculture Department holds jurisdiction over the dairy cows, the FDA is in charge of making sure milk and other foods are safe and the CDC has the responsibility to ensure the safety of farmworkers.
The FDA has repeatedly tested milk on store shelves throughout the country and found no live virus, due to pasteurization, he said.
The agency is interested in testing milk before the pasteurization process begins, though Califf said theyve had some difficulties getting access to dairy farms.
Access to the farms, for example, is really something that has to be negotiated through the states, he said. The farmers and the owners of dairy farms are more comfortable with people that they know that are in their state. So all this has to be coordinated.
Califf explained that when cows are milked, that goes into bulk tanks, which is a mixture of a number of cows.
Thats a very sensitive area because it does point, if there are infected cows, as to where the infections are, Califf testified. And technically its no problem, but we want to make sure we have trust. And so theres negotiation that needs to go on to make sure theres a safe way to handle the data and that people are not going to be castigated if they happen to have an infected herd. So were working through all that state by state.
Wisconsin Democratic Sen. Tammy Baldwin urged the FDA to coordinate and communicate frequently with farmers and the public.
Her home state, she noted, has more than 5,000 dairy herds, making up 22% of the nations total herd count. So this is a big deal for us.
The H5N1 bird flu circulating in the U.S. remains far more dangerous for birds than for people.
Currently, this strain of the flu that circulated in cows has led to just a single person being affected in the last few months. But the strain of influenza has the potential to mutate, so federal health officials are already thinking ahead toward a potential vaccine.
The country has two candidate vaccine viruses available to manufacturers for the production of a bird flu vaccine, the Centers for Disease Control and Prevention (CDC) said on its website.
These [candidate vaccine viruses] are like seed stock that are kept in reserve in case there is an outbreak of that particular strain, said David Diemert, MD, a professor of medicine in the School of Medicine and Health Sciences at George Washington University, and director of the GW Vaccine Research Unit.
If bird flu started easily spreading to people, [the candidate vaccine virus] can be sent to manufacturers to make millions of doses of vaccine, he said, using the existing hen egg technology that we normally use for the regular seasonal vaccine.
A candidate vaccine virus is attenuated, or weakened version of the virus. As a result, it is unlikely to lead to active infections in people who get the vaccine.
This type of weakened virus is able to grow well in hen eggs, which is what most manufacturers use to produce seasonal flu vaccine.
The candidate vaccine would also have the surface proteins known as hemagglutinin of the virus circulating in the community. This enables a vaccine to generate a protective immune response.
The U.S. National Pre-Pandemic Influenza Vaccine Stockpile (NPIVS) has four types of H5N1 candidate vaccine viruses, reported STAT News. The bird flu affecting dairy cows is a strain of H5N1.
Only two of these candidate vaccine viruses are a good match for the currently circulating strain of bird flu.
Studies suggest that vaccines based on these two candidate vaccine viruses will offer good cross-protection against cattle outbreak viruses, Demetre Daskalakis, director of the National Center for Immunization and Respiratory Diseases, said on a call on May 1.
However, Amesh Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health, cautioned that the candidate vaccine viruses are not a perfect match for the currently circulating strain of H5N1. This means they may not produce vaccines very effective at preventing disease.
In addition, research done in the mid-2000s found that H5N1 vaccines dont trigger a strong immune response in people unless it is given in a large enough dose; or if it is given with a compound known as an adjuvant, which boosts the immune response.
Adalja pointed out that the H5N1 vaccines that we have in the stockpile are really not that good at provoking an immune response.
Even for the viruses they are targeted against, said Adalja. In clinical trials, the protective antibody levels that people had were modest.
One of these existing H5N1 vaccines in the NPIVS is made by CSL Seqirus, which supplies flu vaccine to the U.S. market.
Still, Diemert thinks a bird flu vaccine based on the two candidate vaccine viruses in the NPIVS would be effective and potentially more effective than seasonal influenza vaccines.
This is because a bird flu vaccine would likely only have to target a single virus strain.
In contrast, during seasonal flu season, there may be multiple strains of influenza that spread. Seasonal flu vaccines are developed to target certain strains of influenza every year. The vaccines are developed in the summer and early fall by looking at common strains in the Southern Hemisphere. But during flu season the strains that become more common in North America may not be the strains the vaccine was primed to target.
As a result, seasonal flu vaccines may end up targeting strains of influenza virus that are not the ones in circulation that year.
Thats one of the reasons that [seasonal flu vaccines] are not 100% effective because theyre not a perfect match, said Diemert.
Before bird flu vaccines could be rolled out, they would need to be approved by the Food and Drug Administration (FDA) but the agency has a process for approving updated seasonal flu vaccines each year.
So this should go fairly smoothly, said Diemert, especially since the [bird flu] vaccines would be made using the same manufacturing process that they use every year [for seasonal flu vaccines].
Also, Im sure if there was a massive outbreak of this particular strain, then the FDA would speed things up, he said. So I dont see regulatory approval being a rate-limiting step.
In terms of getting the vaccine to the people who need it the most, all of the pieces are in place to be able to roll out a vaccine relatively quickly, said Diemert.
However, when you send [the candidate vaccine virus] to the manufacturer, it still takes weeks to months to make all the doses you need, he said.
This is especially difficult in a fast-moving situation such as a pandemic, said Peter Chin-Hong, MD, an infectious disease physician at UCSF Health.
Federal health officials estimate that over 100 million doses could be shipped within three to four months. However, they expect people to need two doses, so this would only cover 50 million people.
Vaccine production could also be affected by the same virus the vaccine would be designed to protect against.
Manufacturers most often use hen eggs to produce flu vaccines, but chickens are also susceptible to the bird flu virus that is affecting cattle.
So, if you have a global [influenza] pandemic, and you have birds dying too, that may constrain supplies such as chicken eggs, said Adalja.
As of May 6, over 5 million chickens and other commercial or backyard poultry birds in the United States have been affected by highly pathogenic avian influenza (HPAI). which includes H5N1, reports the U.S. Department of Agriculture.
The big question is whether enough vaccine doses could be rolled out in time to make a difference.
With the 2009 H1N1 pandemic, by the time the vaccine came out, the pandemic had already dissipated, said Chin-Hong.
During that outbreak, tens of millions of Americans were vaccinated, but by the time the vaccine doses were available, the fall wave had subsided.
However, this is 2024 and things have changed, said Chin-Hong, referring to the fast development and rollout of the COVID-19 vaccines. When people put their mind to it, it could be done fast But the devil is in the details.
Overall, its going to take some time to actually gear up to be able to vaccinate everybody whos at risk for flu, said Adalja. And as I said, the candidate vaccine virus that is stockpiled is not a perfect match. And even if it were a perfect match, [the H5N1 vaccine] is not a great vaccine to begin with.
Federal health officials said the government is also pursuing an mRNA bird flu vaccine, based on the same technology as Pfizers and Modernas COVID-19 vaccines.
Chin-Hong said this type of vaccine could potentially be updated more quickly to match the currently circulating strains of the virus. But these vaccines have their own challenges, he said, such as needing to be stored at extremely cold temperatures.
In addition, given that these vaccines would be a new use of the mRNA vaccine technology, the FDA may require clinical trials which could delay the roll-out to the greater population.
There are other options for dealing with an outbreak of bird flu in people, including antivirals such as Tamiflu, which would be given to people who are already infected.
Different interventions speak to different people, said Chin-Hong. In general, Americans prefer to treat something rather than prevent it, which can be a challenge.
As seen during the COVID-19 pandemic, its not just how many vaccine doses you can ship that matters, but also how many people receive the vaccines.
The problem we may have is that there is more vaccine hesitancy now, so people may not be as willing to get vaccinated, said Diemert. I dont know if that will be different because the [hen egg] flu vaccine technology has been around for decades and theres a lot of evidence of its safety.
Chin-Hong pointed to the poor current COVID-19 vaccination rates among American adults as a sign of vaccine fatigue.
Around 22% of all American adults have received the updated COVID-19 vaccine, with a slightly better rate (38%) among older adults, according to the CDC. Both rates are much lower than health officials would like to see.
That shows how fatigued people are [with vaccination campaigns], said Chin-Hong. This [hesitancy] would need to be addressed in the same breath as having a well-oiled plan [for rolling out the vaccines].
Adalja is concerned not just about vaccine hesitancy, but with growing public opposition to vaccines, in general.
In 2009 with H1N1, vaccination uptake was subpar because concerns raised by the anti-vaccine community which were unwarranted concerns dissuaded people from getting vaccinated, he said.
But after COVID-19, the anti-vaccine movement is more powerful than it has been in decades, he added. So I think mounting a vaccination campaign in an [future] emergency is going to be very difficult to do in the current political environment.
There is no sign that the H5N1 bird flu circulating in dairy cow herds is developing the ability to spread easily to people. But federal health officials are planning for the rollout of a bird flu vaccine as a precaution.
The federal government has two candidate vaccine viruses stockpiled. These are weakened so they cannot infect people or cause illness, but they grow well in hen eggs, which is how flu vaccine are most often made.
The candidate vaccine viruses are not a perfect match for the bird flu virus currently circulating, but they should offer good protection, say health officials. However, experts are concerned that vaccine fatigue will deter uptake.
Flu likes to bind to a sugar on the surface of cells, and the reason bird influenzas usually doesnt spread among humans is that our sugars are very different, explained Richard Webby, a specialist in influenza at St. Judes Childrens Research Hospital in Memphis.
The cells in a pigs respiratory tract have both kinds of sugars, so both kinds of virus can get in and swap pieces. The infamous 1918 influenza virus, thought to have originated from a bird flu, was transmitted from humans to pigs in the 1920s, where it continued to evolve. It re-emerged in humans in 1957, 1968 and 2009. In recent years, as bird flu surged through domestic flocks, its gained the power to infect dozens of mammal species, including minks, racoons, foxes, seals and porpoises. We really dont want pigs to be next.
Yet the wider the cow infections spread, the more chances the virus has to jump to pigs. They might get infected through contaminated equipment, or if milk from infected cows gets into their feed. Although pasteurization kills the virus in commercial milk, the raw milk remains highly infectious its the lead suspect in deaths of several farm cats infected with H5N1.
Whats a bit unclear to me is exactly whats happening to all this contaminated milk, said Webby. Could some be getting dumped, raw, where other animals could ingest it?
Colorado state officials are working with federal authorities to limit the spread of bird flu among dairy cattle.
The first case of highly pathogenic avian influenza (HPAI) in the state was confirmed April 24 in a dairy herd in northeastern Colorado. During an hour-long webinar Wednesday morning State Veterinarian Dr. Maggie Baldwin noted the affected herd was in the northeast corner of our state, but the Colorado Department of Agriculture declined to say in what county the infection was found.
Screen grab from Colorado Department of Agriculture slide stack.
Screen grab from Colorado Department of Agriculture slide stack.
Screen grab from Colorado Department of Agriculture slide stack.
Screen grab from Colorado Department of Agriculture slide stack.
Colorado is the ninth state in which HPAI has been found in dairy cattle. Baldwin said nobody yet knows for sure how the virus has migrated from birds to cattle, but said viral spillover isnt uncommon. In the wild, for instance, HPAI has been found in skunks, foxes and other mammals, but the April 24 discovery is the first in Colorado among domesticated animals.
It has not been detected in any other livestock species, Baldwin said. We dont know of any concern for beef cattle or other species (of livestock.)
Symptoms can include a drop in milk production, loss of appetite, changes in manure consistency, thickened or colostrum-like milk and low-grade fever. Infected cows seem to recover completely after supportive care.
With fair and livestock show season just around the corner, Baldwin said the U.S. Department of Agriculture hasnt issued guidance yet, but hopes to have some definitive answers soon.
We will get information out as quickly as possible but ask people to be patient with us as we work on that, she said. We dont know what the mechanism of transmission in dairy cattle is, but (there are) a lot of really great people working on studying that to give us a better idea of that.
The virus was first detected in March in dairy herds in Texas and Kansas. By late April the virus had showed up in North Carolina, Ohio, Michigan, South Dakota, Colorado, New Mexico and Idaho. The nine-state outbreak in prompted the USDA to issue strict guidelines on April 29 on the movement of dairy cows, especially across state lines. According to that directive, prior to interstate movement, lactating dairy cattle will be required to receive a negative result of testing for influenza type A virus, as performed by an approved National Animal Health Laboratory Network laboratory.
The federal order can be read in detail at the CDOAs website ag.colorado.gov/HPAIcattle. The website also contains detailed information on maintaining biosecurity in dairy herds.
Dr. Rachel Herlihy, the state epidemiologist for the Colorado Department of Public Health and Environment, said the risk of spread to humans is low, but could depend on how much a person is exposed to the virus. She said one person was confirmed with HPAI in Colorado in 2022 and another more recently in Texas. Both cases were very mild, Herlihy said, which indicates that the virus has not yet adapted for human-to-human transmission.
While the virus does show up in an infected cows milk, there is no danger to human transmission. Herlihy said pasteurization continues to be effective in killing virus and bacteria in milk.
HPAI has been a concern for several years but mostly among commercial and back-yard poultry flocks. Millions of commercial birds have had to be destroyed because of outbreaks on poultry farms. The virus is easily transmitted among birds of all types, though some that carry the disease show no symptoms from it. So far HPAI has showed up in 48 states on 1,129 properties and has killed more than 10,000 snow geese, 2,200 Canada geese and 150 raptors and avian scavengers.
As agricultural authorities and epidemiologists try to get their arms around the scope of the latest confounding chapter in the decades-long story of the H5N1 avian influenza virus its jump into U.S. herds of dairy cattle theyre turning to the genetic breadcrumbs the virus leaves behind in the animals nose, lungs, and, primarily, milk.
On Wednesday, U.S. Department of Agriculture scientists released a preprint a study that has not yet been peer-reviewed describing for the first time what their investigations of 220 viral genomes from infected cows have so far turned up. The studys authors suggest that the spread in cattle started from a single spillover event from birds in the Texas panhandle that may have happened in early December. The USDA didnt confirm the presence of H5N1 in a Texas herd until March 25.
These data support a single introduction event from wild bird origin virus into cattle, likely followed by limited local circulation for approximately 4 months prior to confirmation by USDA, the authors wrote.
The findings add more precision to what had previously been reported by academic scientists. Reading viral genomes can provide clues to the origins of the outbreak and allows researchers to monitor how the virus, which primarily infects wild and farmed birds, is changing as it finds a foothold in bovine hosts.
In an initial analysis of USDA genome sequence data released last week, academic DNA sleuths had revealed that the outbreak in dairy cows has likely been going on for months longer than previously realized, and has probably spread more widely than official numbers would suggest. So far, the USDA has reported 36 herds in nine states have tested positive for the virus.
The new analysis also offers a window into how the bird flu is changing as it spends time in the bodies of cattle.
In the last few years, H5N1 has spread from wild birds to a variety of carnivorous mammals, including foxes, bears, and seals, but in each of those instances, the virus has hit a dead end. The outbreak in dairy cows represents one of the first times that this bird flu virus has demonstrated the ability to efficiently transmit between mammals, said Thomas Mettenleiter, a virologist who served as the director of the Friedrich Loeffler Institut Germanys leading animal disease research center from 1996 until he stepped down last year. The other instance was a number of outbreaks at mink farms in Spain and Finland in 2022 and 2023, respectively.
These spillover events dont usually lead to transmission chains, he said. This situation is definitely an eye-opener for me.
The USDAs analysis found about two dozen mutations that have arisen in the H5N1 virus as it has circulated in dairy cattle that are known to make influenza viruses more deadly or more likely to be able to infect humans.
Its still really difficult to draw a risk map out of that, but there seems to be ongoing evolution, Mettenleiter said. This is not surprising but its good to know. All these mammal-to-mammal passages, as we would do experimentally, put an evolutionary pressure on the virus to mutate and this is what we see with the increase of these known mammalian adaptation markers.
Vivien Dugan, director of the influenza division at the Centers for Disease Control and Prevention, told STAT Thursday that the mutations found so far did not raise any immediate red flags for increased risk to human health.
I think based on our analysis of the consensus and some of that raw [sequence] data because we have a good data-sharing relationship with USDA weve not seen anything that would be concerning to us for mammalian adaptation, at this point, Dugan said.
The CDC has been testing existing H5 vaccines in ferrets, and found that vaccination appears to offer cross-protection against the virus from the man who was infected in Texas.
Scientists who have been frustrated by the slow drip of data from the USDAs investigations hailed the preprint on social media as progress. Really grateful to this research team for sharing this, though I hope they werent holding on to the data solely to ensure they published first, Angela Rasmussen, a virologist who studies pathogens that jump from animals to people at the Vaccine and Infectious Disease Organization at the University of Saskatchewan, in Saskatoon, Canada, posted on X on Thursday.
For weeks, the agency has been facing criticism from scientists and pandemic expertsfor a lack of transparency and timely sharing of data about the outbreak that has slowed down efforts to track its progress. When the USDA finally uploaded a large tranche of genetic sequences of the pathogen to a public database, researchers eager to analyze the sequences to determine if the H5N1 virus has been changing as it is transmitted from cow to cow quickly discovered that the sequences didnt include necessary information about when and where the samples were collected. All are simply labeled with USA and 2024.
The USDA has denied taking that basic information called metadata off the sequence files. The agencys Animal and Plant Health Inspection Service has said it is sharing raw sequence data as quickly as it is available and plans to upload consensus sequences, which are more thoroughly edited and contain the metadata scientists are seeking, when they are ready.
Helen Branswell contributed reporting.
A new report on the first human bird flu case tied to the outbreak in cows in the United States suggests that the Texas man may be the first detected case of the H5N1 virus transmitting from a mammal to a person.
Nearly 900 people in 23 countries have been infected with the H5N1 bird flu virus since it started spreading from Southeast Asia in late 2003. But previous human cases were all linked to transmission from infected birds, typically domestic poultry.
The report, published Friday by the New England Journal of Medicine, details the unidentified mans symptoms and his possible route of infection. It was written by scientists from the Centers for Disease Control and Prevention, the Texas Department of State Health Services, and the Texas Tech University Bioterrorism Response Laboratory in Lubbock. The senior author was Tim Uyeki, chief medical officer of the CDCs influenza division, who has investigated H5N1 outbreaks around the world for more than 20 years.
How the man became infected cannot be proven; while the cattle on the farm where he worked reportedly suffered from a decline in milk and other symptoms seen in herds that have tested positive for H5N1, no animal testing at that farm was undertaken. The authors noted, though, that nearby farms where dairy cows experienced the same symptoms tested positive for the virus.
Further reading
Given the infected human was a dairy farm worker with reported exposure to sick, presumably infected cows in Texas and without reported exposure to other mammals or birds, we believe the genetic and epidemiologic data are strong evidence of infection of the human following exposure to presumably HPAI A(H5N1) virus-infected cows, they wrote in the supplementary materials that accompanied their report.
HPAI A(H5N1) is scientific shorthand for highly pathogenic avian influenza A virus of the H5N1 subtype. The term highly pathogenic applies only to how the virus behaves when it infects poultry, though people might easily assume it applies more broadly, given how deadly this virus has proven to be over the decades. Roughly half of the people known to have been infected died. It kills wild birds and dozens of mammalian species, including cats (domestic and large cats), seals, foxes, mink, and many other scavenging carnivores that have had the misfortune of consuming infected wild birds.
In the report the authors describe, the mans illness was exceedingly mild. His lungs were clear and he had no trouble breathing; he had no fever. His sole symptom appeared to be conjunctivitis, a condition colloquially known as pink eye.
The man and people he lived with were given flu antiviral drugs. He reported that his conjunctivitis cleared up. None of the people he lived with became sick.
Ideally in cases like this, scientists would draw blood from the man and his contacts, as well as from other people working on the farm, to look for antibodies to the H5N1 virus. Presence of antibodies among other farm workers might suggest the virus is passing to people more commonly than has been seen. Antibodies in the blood of the mans contacts could indicate that he transmitted the infection to them, but that their cases were so mild they didnt have symptoms.
But this work was not done, the report said, because the man and his contacts would not agree to have blood drawn. We were also unable to collect acute or convalescent sera to assess seroconversion in the dairy farm worker or household contacts, they said. Likewise it appears that health authorities were not allowed on the farm to investigate whether more workers might have been infected.
The authors report that nasal swabs taken from the man also showed presence of virus, but at much lower levels than what was found in his conjunctiva, the tissue surrounding the eye.
They hypothesize that the man could have been infected by one of two routes. Either virus in the air in the milking parlor landed in his eyes reportedly he did not wear eye protection or he may have had virus on his hands or gloves and transferred it to his eye inadvertently, they suggested.
Analysis of the genetic sequence of the virus retrieved from this man has shown that while it is closely related to the viruses that have been causing the cow outbreaks, it does not fit neatly into the viral family tree that scientists studying the sequences have developed. The authors suggested that its possible the virus was from a slightly different offshoot that has died off; alternatively, there could have been more than one spillover event from birds in the Texas panhandle region where these outbreaks were first observed.
To date, 36 herds in nine states have tested positive for the virus, though it is believed that many more have experienced outbreaks but have not been tested. Both the U.S. Department of Agriculture and the CDC have acknowledged that farmers have often refused to cooperate with their efforts to investigate these outbreaks.
The report noted that the virus from the man was closely related, genetically, to the viruses used to produce two batches of H5N1 vaccine that the U.S. government has made and stockpiled as a hedge against a bird flu pandemic. The stockpiled vaccine, of which there are about 10 million doses, would likely afford immune protection in people if used as vaccines, the authors concluded.
In its latest updates, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) reported more H5N1 avian flu detections in poultry and wild birds, including several pigeons in Michigan's Ionia County, an area where the virus has been reported in dairy cows.
In other US developments, a top official from the Centers for Disease Control and Prevention (CDC) yesterday urged state health and veterinary officials to ensure that personal protective equipment (PPE) is available to workers on dairy farms, poultry farms, and slaughterhouses.
APHIS yesterday reported 16 more H5N1 detections in wild birds, half of them rock pigeons that the agency harvested from Michigan's Ionia County, one of the state's five counties that has reported the virus in dairy herds.
In some instances, the B3.13 genotype circulating in dairy cows has jumped to wild birds and poultry. APHIS data so far, however, indicates that the Ionia County samples belong to the Eurasian H5N1 lineage.
The agency also reported the virus in birds found dead in three other statesNew Mexico, Pennsylvania, and Virginia. All are linked to the Eurasian H5N1 strain.
Samples for the latest batch of wild bird samples were collected in mid to late April.
In other developments, APHIS reported one more outbreak in poultry, which involves a flock of 600 birds in Idaho's Cassia County, which last month reported H5N1 in a dairy herd. Idaho's State Department of Agriculture said the location had backyard birds.
Yesterday the CDC's principal deputy director, Nirav Shah, JD, MD, had a call with state health officials and veterinarians, as well as leaders from public health partners, to discuss PPE for farm workers, according to CDC's readout of the meeting. Along with a request to make PPE available to farm workers, Shah recommended that PPE be prioritized to farms where H5N1 has been detected in dairy cows.
He asked states to use their existing PPE stockpiles and told them how to request more PPE, if needed, from the federal government's Strategic National Stockpile.
The CDC reiterated that the general risk to the US public remains low, but it noted that people with work exposures may be at higher risk.
Shah also said the CDC remains ready to support state health officials who are conducting outbreak response operations.
Headlines are flying after the Department of Agriculture confirmed that the H5N1 bird flu virus has infected dairy cows around the country. Tests have detected the virus among cattle in nine states, mainly in Texas and New Mexico, and most recently in Colorado, said Nirav Shah, principal deputy director at the Centers for Disease Control and Prevention, at a May 1 event at the Council on Foreign Relations.
A menagerie of other animals have been infected by H5N1, and at least one person in Texas. But what scientists fear most is if the virus were to spread efficiently from person to person. That hasnt happened and might not. Shah said the CDC considers the H5N1 outbreak a low risk to the general public at this time.
Viruses evolve and outbreaks can shift quickly. As with any major outbreak, this is moving at the speed of a bullet train, Shah said. What well be talking about is a snapshot of that fast-moving train. What he means is that whats known about the H5N1 bird flu today will undoubtedly change.
With that in mind, KFF Health News explains what you need to know now.
Mainly birds. Over the past few years, however, the H5N1 bird flu virus has increasingly jumped from birds into mammals around the world. The growing list of more than 50 species includes seals, goats, skunks, cats, and wild bush dogs at a zoo in the United Kingdom. At least 24,000 sea lions died in outbreaks of H5N1 bird flu in South America last year.
What makes the current outbreak in cattle unusual is that its spreading rapidly from cow to cow, whereas the other cases except for the sea lion infections appear limited. Researchers know this because genetic sequences of the H5N1 viruses drawn from cattle this year were nearly identical to one another.
The cattle outbreak is also concerning because the country has been caught off guard. Researchers examining the viruss genomes suggest it originally spilled over from birds into cows late last year in Texas, and has since spread among many more cows than have been tested.
Our analyses show this has been circulating in cows for four months or so, under our noses, said Michael Worobey, an evolutionary biologist at the University of Arizona in Tucson.
Not yet. But its a thought worth considering because a bird flu pandemic would be a nightmare. More than half of people infected by older strains of H5N1 bird flu viruses from 2003 to 2016 died. Even if death rates turn out to be less severe for the H5N1 strain currently circulating in cattle, repercussions could involve loads of sick people and hospitals too overwhelmed to handle other medical emergencies.
Although at least one person has been infected with H5N1 this year, the virus cant lead to a pandemic in its current state. To achieve that horrible status, a pathogen needs to sicken many people on multiple continents. And to do that, the H5N1 virus would need to infect a ton of people. That wont happen through occasional spillovers of the virus from farm animals into people. Rather, the virus must acquire mutations for it to spread from person to person, like the seasonal flu, as a respiratory infection transmitted largely through the air as people cough, sneeze, and breathe. As we learned in the depths of Covid-19, airborne viruses are hard to stop.
That hasnt happened yet. However, H5N1 viruses now have plenty of chances to evolve as they replicate within thousands of cows. Like all viruses, they mutate as they replicate, and mutations that improve the viruss survival are passed to the next generation. And because cows are mammals, the viruses could be getting better at thriving within cells that are closer to ours than birds.
The evolution of a pandemic-ready bird flu virus could be aided by a sort of superpower possessed by many viruses. Namely, they sometimes swap their genes with other strains in a process called reassortment. In a study published in 2009, Worobey and other researchers traced the origin of the H1N1 swine flu pandemic to events in which different viruses causing the swine flu, bird flu, and human flu mixed and matched their genes within pigs that they were simultaneously infecting. Pigs need not be involved this time around, Worobey warned.
Cows milk, as well as powdered milk and infant formula, sold in stores is considered safe because the law requires all milk sold commercially to be pasteurized. That process of heating milk at high temperatures kills bacteria, viruses, and other teeny organisms. Tests have identified fragments of H5N1 viruses in milk from grocery stores but confirm that the virus bits are dead and, therefore, harmless.
Unpasteurized raw milk, however, has been shown to contain living H5N1 viruses, which is why the FDA and other health authorities strongly advise people not to drink it. Doing so could cause a person to become seriously ill or worse. But even then, a pandemic is unlikely to be sparked because the virus in its current form does not spread efficiently from person to person, as the seasonal flu does.
A lot! Because of a lack of surveillance, the U.S. Department of Agriculture and other agencies have allowed the H5N1 bird flu to spread under the radar in cattle. To get a handle on the situation, the USDA recently ordered all lactating dairy cattle to be tested before farmers move them to other states, and the outcomes of the tests to be reported.
But just as restricting Covid tests to international travelers in early 2020 allowed the coronavirus to spread undetected, testing only cows that move across state lines would miss plenty of cases.
Such limited testing wont reveal how the virus is spreading among cattle information desperately needed so farmers can stop it. A leading hypothesis is that viruses are being transferred from one cow to the next through the machines used to milk them.
To boost testing, Fred Gingrich, the executive director of a nonprofit organization for farm veterinarians, the American Association of Bovine Practitioners, said the government should offer funds to cattle farmers who report cases so that they have an incentive to test. Barring that, he said, reporting just adds reputational damage atop financial loss.
These outbreaks have a significant economic impact, Gingrich said. Farmers lose about 20% of their milk production in an outbreak because animals quit eating, produce less milk, and some of that milk is abnormal and then cant be sold.
The government has made the H5N1 tests free for farmers, Gingrich added, but they havent budgeted money for veterinarians who must sample the cows, transport samples, and file paperwork. Tests are the least expensive part, he said.
If testing on farms remains elusive, evolutionary virologists can still learn a lot by analyzing genomic sequences from H5N1 viruses sampled from cattle. The differences between sequences tell a story about where and when the current outbreak began, the path it travels, and whether the viruses are acquiring mutations that pose a threat to people. Yet this vital research has been hampered by the USDAs slow and incomplete posting of genetic data, Worobey said.
The government should also help poultry farmers prevent H5N1 outbreaks since those kill many birds and pose a constant threat of spillover, said Maurice Pitesky, an avian disease specialist at the University of California-Davis.
Waterfowl like ducks and geese are the usual sources of outbreaks on poultry farms, and researchers can detect their proximity using remote sensing and other technologies. By zeroing in on zones of potential spillover, farmers can target their attention. That can mean routine surveillance to detect early signs of infections in poultry, using water cannons to shoo away migrating flocks, relocating farm animals, or temporarily ushering them into barns. We should be spending on prevention, Pitesky said.
No one really knows. Only one person in Texas has been diagnosed with the disease this year, in April. This person worked closely with dairy cows, and had a mild case with an eye infection. The CDC found out about them because of its surveillance process. Clinics are supposed to alert state health departments when they diagnose farmworkers with the flu, using tests that detect influenza viruses, broadly. State health departments then confirm the test, and if its positive, they send a persons sample to a CDC laboratory, where it is checked for the H5N1 virus, specifically. Thus far we have received 23, Shah said, all but one of those was negative.
State health department officials are also monitoring around 150 people, he said, who have spent time around cattle. Theyre checking in with these farmworkers via phone calls, text messages, or in-person visits to see if they develop symptoms. And if that happens, theyll be tested.
Another way to assess farmworkers would be to check their blood for antibodies against the H5N1 bird flu virus; a positive result would indicate they might have been unknowingly infected. But Shah said health officials are not yet doing this work.
The fact that were four months in and havent done this isnt a good sign, Worobey said. Im not super worried about a pandemic at the moment, but we should start acting like we dont want it to happen.
Amy Maxmen | KFF Health News
Amy Maxmen | KFF Health News
