An unusual bird flu outbreak in dairy cows has now affected at least 13 herds in six states, according to federal and state officials. These infections represent the first time that a highly pathogenic bird flu virus, which is often fatal in birds, has been detected in U.S. cattle.
At least one person in Texas has been diagnosed with bird flu after having contact with dairy cows presumed to be infected, state officials said on Monday. The patients primary symptom was conjunctivitis; the individual is being treated with an antiviral drug and is recovering, according to the Centers for Disease Control and Prevention.
The virus has been identified as the same version of H5N1, an influenza subtype, that is circulating in North American birds. Scientists have not found evidence that the virus has acquired the mutations it would need to spread easily between humans, officials have said.
The risk to the general public remains low, experts said. But these developments add a worrying dimension to an avian influenza outbreak that has already affected millions of birds and sea mammals worldwide.
Heres what to know:
Bird flu, or avian influenza, is a group of flu viruses that are primarily adapted to birds. The particular virus in these new cases, called H5N1, was first identified in 1996 in geese in China, and in people in Hong Kong in 1997.
In 2020, a new, highly pathogenic form of H5N1 emerged in Europe and spread quickly around the world. In the United States, it has affected more than 82 million farmed birds, the worst bird flu outbreak in U.S. history.
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A person in Texas is being treated for avian influenza (bird flu), according to a report from state officials. The deadly virus has sickened dairy cows in five states in recent weeks.
This marks the first known instance globally of a person catching the H5N1 strain of bird flu from a mammal and just the second human case of the illness in the United States, according to the Centers for Disease Control and Prevention (CDC). An individual who had contact with infected poultry caught the virus in 2022.
Dean Blumberg, chief of pediatric infectious diseases at UC Davis Health, answers questions about what you need to know about bird flu.
Bird flu is caused by influenza strains that commonly infect wild birds worldwide. They can also cause outbreaks among commercial or backyard poultry, and less commonly other animals.
Bird flu may cause birds to have respiratory symptoms such as a runny nose and coughing or sneezing, diarrhea, less energy, decreased egg production, or sometimes sudden death.
In humans, bird flu may cause illnesses similar to influenza (the flu) with fever, cough, sore throat, runny nose and muscle aches. Less commonly, humans may have diarrhea and vomiting, and more rarely, seizures.
Most infections occur when humans have contact with sick or dead infected animals without wearing personal protective equipment.
Many different bird species may be infected with bird flu, and the infectious virus is shed in their saliva, mucous and feces. The shed infectious virus may then infect other animals, including cows.
Bird flu rarely spreads person-to-person. It is more commonly spread from animal to human. There has been no evidence of sustained human-to-human spread.
There is no evidence bird flu is currently more easily spread human-to-human, although there is always a chance the virus may evolve to more easily transmit among humans. Most human infections with bird flu can be traced to unprotected close contact with ill or dead animals.
Sick or ill animals should be culled, and their animal products should not be sold. Pasteurization will kill infectious virus in contaminated milk. There may be a risk of transmission if unpasteurized milk from an ill animal is ingested.
Bird flu is treated similarly to influenza in humans. The antiviral oseltamivir (Tamiflu) remains an effective option to treat humans infected with bird flu.
Avoid unprotected exposures to sick or dead animals. This includes birds, poultry or other animals. For those who work with animals, full personal protective equipment should be used when in close or direct contact with animals or material that is potentially contaminated with the virus. This includes an N95 mask or equivalent, goggles, gloves, gown, head cover and boot covers.
This article first appeared in The Checkup, MIT Technology Reviews weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here.
A dairy worker in Texas tested positive for avian influenza this week. This new human case of bird fluthe second ever reported in the United Statesisnt cause for panic. The individuals illness was mildan eye infectionand they are already recovering. Theres still no evidence that the virus is spreading person to person. The person who became infected in Texas likely picked the virus up from infected cows or poultry on the farm where he works.
But the rash of recent infections among livestock is unsettling. Last month, goats in Minnesota tested positive. And avian influenza has now been confirmed in dairy cows in Texas, Michigan, Kansas, New Mexico, and Idaho. In some of those cases, the virus appears to have spread between cows. This week, lets take a look at what we know about this new outbreak and what people are doing to prepare for further spread.
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The strain of flu infecting dairy cowsH5N1is a highly pathogenic avian influenza. Scientists have been watching these viruses closely since the 1990s because of their potential to spark a pandemic. In 1997, avian influenza sickened humans for the first time. Eighteen people in Hong Kong became infected, and six died.
Small spillovers into mammals arent uncommon for these viruses, especially in recent years. Avian influenza has been reported in mink, skunks, raccoons, coyotes, seals, sea lions, and bears, to name a few. But having the virus in domesticated mammals that come into frequent contact with humans is new territory. Exactly what happens when an avian flu virus replicates in a cow and potentially transmits from cow to cow, we actually dont have any idea at all, says Richard Webby, a virologist at St. Jude Childrens Research Hospital who studies avian influenza.
Heres the good news: even though the virus is infecting dairy cows (and now one dairy worker), this is still very much a bird virus, Webby says. Genetic sequencing by the USDA and the Centers for Disease Control suggests that these new infections are caused by a strain of flu thats nearly identical to the virus circulating in wild birds. Few of the changes they did identify would allow it to spread more easily in mammals.
The spread of bird flu in cows is worrisome, but not as worrisome as it would be if the infections were happening in pigs, which are an ideal mixing vessel for flu virus. Pigs are susceptible to swine flu, avian influenza, and human influenza. Thats how swine flu emerged back in 2009multiple viruses infecting pigs swapped genes, eventually giving rise to a virus capable of human transmission.
Mammalian infections with bird flu have mostly been one-offs, Webby says. A mammal gets infected by eating a dead bird or ingesting bird droppings, but the infection doesnt spread. One notable exception occurred in 2022, when H5N1 popped up on a mink farm in Spain and quickly jumped from barn to barn. Scientists also suspect that in rare cases, the virus has spread among family members.
Cow-to-cow transmission hasnt been confirmed, but the fact that some cows became infected after the arrival of cows from affected herds suggests that it may be occurring. That transmission may not be via coughs and sneezesthe traditional way flu gets passed on. It could be indirect. So an infected cow drinks from a trough of water and the next cow comes along and drinks from that same trough, Webby says.
How can we curb the spread among animals? Thats an ongoing debate. Vaccination is an option, at least for poultry. Thats common practice in China, Mexico, and a handful of other countries. Immunization doesnt prevent infection, but it does reduce symptoms. That might curb the impact on flocks, but some experts are concerned that vaccinated flocks might allow the virus to spread undetected. Vaccination also would likely affect trade. Countries dont want to import birds that might be infected. France decided to begin vaccinating ducks last year, and the USDA promptly announced it would restrict poultry imports from France and its trading partners. In the US, the current practice is to cull infected flocks. But there are signs that vaccination isnt off the table. Last year the USDA began testing four vaccine candidates against the particular strain of H5N1 driving the current outbreak that has affected poultry across the globe.
As a longer-term solution, researchers have also been working on creating genetically engineered animals that are resistant to bird flu. Last year, researchers created such chickens by using CRISPR to alter a single gene.
For cattle, the current options to curb transmission are limited. Culling cattle would be a much harder sell because theyre so much more valuable than chickens. And cow vaccines for avian influenza dont yet exist, although they would be relatively easy to produce.
Bird flu has been on public health officials radar for more than two decades, and it has yet to make a jump into humans. I do think that this particular virus has some fairly high hurdles to overcome to become a human-transmissible virus, Webby says. But just because it hasnt happened doesnt mean it wont: We can be a little bit reassured that its not easy, but not assured that it cant do it at all.
Luckily, even if the virus suddenly acquired the ability to spread in humans, it would be vastly easier to develop a vaccine than it was to create one for covid-19. A vaccine already exists against H5N1. Doses of that shot are sitting in the countrys national stockpile. This is one case were a little luckier because its a pathogen that we know. We know what this is and what we have in the freezer, so to speak. We have a little bit of a leg up on at least getting started, Paul Marks, the FDAs top vaccine regulator, told a reporter at the World Vaccine Congress this week.
Its not clear how well those doses would work against the current strain of H5N1. But many companies are already working on improved vaccines. Moderna plans to test an mRNA vaccine against the H5N1 strain causing the current outbreak. mRNA technology has a major advantage over traditional production methods for influenza vaccines, which grow the virus in eggs. In the event of a bird flu pandemic, eggs could be in short supply. Even if enough eggs were available, it could take half a year to develop a vaccine. mRNA technology, however, could shorten that timeline dramatically.
Thats good news. With avian influenza surging across the globe, there are more opportunities than ever before for the virus to hit on a combination of genes that gives it the ability to easily infect humans.
In a previous issue of The Checkup, Jessica Hamzelou explained what it would take for bird flu to jump to humans and why we dont need to panic. Not yet, anyway.
Google Earth can help scientists visualize the movement of H5N1 and perhaps even improve our ability to predict where outbreaks might occur. Rachel Ross had the story.
Dig deep into the archives and youll find that Tech Review has been asking if bird flu will jump to humans for nearly two decades. Emily Singer reported on efforts to answer this question in 2006.
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The countrys largest egg producer detected bird flu in its flocks and culled nearly 2 million birds. (Washington Post)
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The FDA has cleared the first prescription digital therapy for depression. The treatment, which is intended to be paired with medication, is an app that provides cognitive-emotional training and cognitive behavioral therapy lessons. (CNN)
A dairy worker in Texas has tested positive for avian influenza, the Centers for Disease Control and Prevention (CDC) confirmed Monday.
The announcement comes just a week after the United States Department of Agriculture (USDA) first announced avian flu outbreaks in certain dairy cow herds in Texas.
Its uncommon for humans to catch the H5N1 subtype avian influenzaalso known as H5N1 bird fluand the CDC said this case is only the second one reported in the U.S. The first case was in Colorado in 2022.
The H5N1 bird flu is often found in wild bird populations, and sick birds can sometimes pass the virus to livestock or other mammals.
In this most recent case, the person in Texas likely became infected after coming in close contact with sick cattle, health officials said.
The case is relatively mild; the CDC said the patient has eye redness (conjunctivitis) but has no other symptoms. The person is being treated with an antiviral for flu, and is isolating.
This infection does not change the H5N1 bird flu human health risk assessment for the U.S. general public, which CDC considers to be low, the agency said in a press release. It acknowledged, however, that people who come into more frequent contact with possibly infected birds or other animals have a higher risk.
Since 2022, bird flu has been detected in wild, commercial, and hobbyist bird flocksin total, over 82 million birds have been affected across 48 states and 512 counties. These outbreaks can cause issues for farmerson Tuesday, Cal-Maine Foods, Inc., the countrys largest egg producer and distributor, culled nearly 2 million hens after an outbreak of avian flu at one of its facilities.
The USDA also found herds of dairy cows testing positive for bird flu in Kansas, Texas, Michigan, and New Mexico. Its assuming a herd in Idaho will test positive, too.
That worries me, because humans interact pretty closely with dairy cattle, said Jill Foster, MD, professor of pediatric infectious diseases at the University of Minnesota Medical School. Youve got these dairy cows now that are infected, and people in the barn [are] pretty close with the dairy cowsI think that theres probably going to be more spread to humans.
Heres what to know about bird flu, how it spreads between animals and humans, and what this infection means for public health.
Tim Graham / Getty Images
This particular type of avian fluH5N1is one of many different subtypes of influenza A. Its still the same influenza that humans get, but the naming refers to slight differences in proteins, Foster told Health.
Certain types of influenza A can lead to pandemics, such as the H1N1 swine flu in 2009 and the H1N1 Spanish flu in 1918 (which was later determined to be an avian-like virus.)
This is what infectious disease experts have feared happening since this H5N1 virus started causing outbreaks among wild birds and poultry in late 2021, Foster explained.
Luckily, however, this current strain of bird flu doesnt seem to be mutating and making jumps into human populations in the same way as other problematic viruses, she said.
[The bird flu] seems to be something that just simmers and spreads quite easily. But it doesnt seem to be one that changes a lot, the way that COVID [does], said Foster. Bird flu has been around for a couple of years, but has stayed mostly in the birds.
Though it can spread easily between birds and other animals, the H5N1 flu virus does not seem to be very efficient at transmitting between animals and humans or from human to human, Foster added. Whereas increasing COVID infections provided more opportunities for the virus to mutate and better evade our immune systems, the same cannot be said for H5N1, at least for now.
In fact, limited spread between humans hasnt been reported since 2007, and theres no evidence that the bird flu could have sustained transmission in human populations.
However, when people do get sick with bird flu, it can be a cause for concern. Some people are asymptomatic or have mild infections, where theyll experience conjunctivitis or flu-like upper respiratory symptoms. But others will have more serious cases that can lead to pneumonia, fever, body aches, shortness of breath, and in very rare cases, diarrhea, nausea, or seizures.
Since 2021, hospitalizations linked to various strains of bird flu have been reported in China and Cambodia, and China has reported over a dozen deaths.
People who get sick with bird flu can be treated with the antiviral Tamiflu (oseltamivir), which works against influenza A.
Because the risk to the general public in connection with this confirmed bird flu case is low, the average person doesnt need to be too worried about contracting the H5N1 virus.
Human infection based on close occupational exposure to a sick animal is of course important to know about, but is also very different than the case of human-to-human transmission, which would be a concern for public health, Sarah Hamer, PhD, DVM, director of the Schubot Center for Avian Health and professor of epidemiology at the Texas A&M University School of Veterinary Medicine and Biomedical Sciences, told Health.
However, those who may be coming into contact with sick poultry or dairy cows could be seeing a higher risk. As soon as you start getting cases, youre going to have more spread, Foster said.
Because of this, the CDC recommends anyone who could be coming into contact with ill or dead animals use proper personal protective equipment (PPE), including vented safety goggles, disposable gloves, boots, masks, disposable coveralls, and a head covering.
PPE is a big one. And then its just re-emphasizing things like proper hand hygiene, washing your hands frequently, if youre not feeling well, staying home, said Mike Kleinhenz, DVM, PhD, clinical associate professor of dairy cattle production at Texas A&M University School of Veterinary Medicine and Biomedical Sciences. Just reinforcing some of those good hygiene practices is important for dairy farmers to dofor their employees and for themselves.
As for where the average person comes into contact with dairythe grocery storetheres also little cause for concern.
Theres no risk of people accidentally getting bird flu from consuming cows milk or other dairy products, so long as its pasteurized, the Food and Drug Administration (FDA) said. That process is able to effectively kill viruses such as influenza.
And though transmission among cows is something experts are monitoring, for now, theres no evidence that bird flu could lead to any major disruptions in the U.S. dairy market, Kleinhenz told Health.
From what were seeing on farms that are affected by this, [its] a small percentage of the cows that are actually becoming infected, and having to have their milk diverted from the saleable pool, he said. For the overall milk supply, we dont expect to have shortages.
H5N1 is a type of influenza virus that causes severe respiratory disease in birds but has occasionally been known to jump to humans as well.
Bird flu is '100 times worse than the Covid pandemic', a report by Daily Mail stated. According to the UK-based tabloid, bird flu can lead to high fatalities. Several scientists have raised alarm over the latest bird flu outbreak in the US.
Dr Suresh Kuchipudi, bird flu researcher in Pittsburgh told Daily Mail, "We are not really talking about a virus that is yet to make a jump, we are talking about a virus that is globally present, already infecting a range of mammals and is circulating." He added that it is high time that people get prepared.
Another expert John Fulton said: "This appears to be 100 times worse than Covid, or it could be if it mutates and maintains its high case fatality rate."
He added that if the flu infects humans, then there is only hope that the fatality rate drops.
Bird flu
The bird flu virus that is now drawing attention was first identified in 1959. Since 2020, the virus has spread among more animal species including dogs and cats in several countries.
The symptoms of bird flu are like any other flu, including cough, body aches, and fever. However, some people may even develop severe, life-threatening pneumonia.
Since 2022, there have been two documented instances of avian influenza, commonly known as bird flu, being transmitted to humans in the United States. One notable case included a farm worker based in Texas who displayed symptoms indicative of bird flu exposure such as conjunctivitis. According to various media outlets, avian influenza has led to deadly infections among individuals exposed regularly to either domestic or wild birds.
The H5N1 strain, presently accountable for the reported cases, has not yet reached a level of virulence that would easily facilitate extensive human transmission. Nonetheless, scientific experts continue to diligently monitor its potential evolutionary trajectory which could significantly enhance its contagion capacity among humans, thereby creating a possibility for a worldwide outbreak.
Bird flu vaccine for humans
The US has a stockpile of vaccines matched with the strain of bird flu currently circulating, as well as antivirals that could be used to treat human infections. The US Centers for Disease Control and Prevention (CDC) also has sample or "seed" strains of the virus that manufacturers could use to make more vaccines.
Pharma giants such as Sanofi and GlaxoSmithKline are also monitoring avian flu to develop avian flu vaccines as and when the need arises.
Editor's note: This is a developing story and will be updated.
A bird flu virus called H5N1 recently infected animals that it had never been seen in before: goats and cows.
Now, it's suspected that a person has picked up the infection after being exposed to infected cows.
Here's what we know so far about these unusual cases of H5N1 in the U.S.
Related: 21-year-old student dies of H5N1 bird flu in Vietnam
H5N1 is a subtype of avian influenza A, a broad group of related bird flu viruses. It's categorized as a form of "highly pathogenic" avian influenza, or HPAI, because it causes severe and fatal disease in poultry. For example, H5N1 and other "H5" bird flu viruses can rapidly cause organ damage in chickens and kill up to 90% to 100%of chickens they infect, often within 48 hours, according to the Centers for Disease Control and Prevention (CDC). H5N1 has been responsible for the major bird flu outbreaks seen on U.S. poultry farms and on farms in other countries since 2022.
Although HPAI viruses are known for devastating domestic bird populations, H5N1 also infects wild birds and occasionally infects various mammals, including people. In non-avian species, it can still cause fatal disease, but some cases are mild or asymptomatic.
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H5N1 infections in mammals, in general, raise concern that the virus could evolve to infect humans more easily and perhaps spread widely between people, sparking a pandemic, according to the World Health Organization (WHO). But scientists haven't seen any changes in the virus that suggest that's happening at this point.
H5N1 most often infects domestic and wild birds, although some wild birds act as "reservoirs" for the virus, meaning they can carry and spread it without getting sick. These carriers include waterfowl, such as ducks, geese and swans; and shorebirds, such as plovers and sandpipers, the CDC says.
In the past 20 years or so, H5N1 has also been detected in at least 48 mammal species across 26 countries. These include foxes, bears, seals, sea lions and polar bears, as well as pet cats and dogs and farmed mink. The U.S. Department of Agriculture (USDA) maintains a map of where different mammals have been infected in the U.S.
This year, for the first time, H5N1 was detected in goats and cows. This marks the first time H5N1 has been found in ruminants, which include hooved, cud-chewing mammals like cows, goats and sheep.
The infections among goats were reported in mid-March on a Minnesota farm where ducks and chickens had previously tested positive for the virus. The first infections in cattle were reported a week later among dairy cows in Texas and Kansas, which also likely got the virus from birds.
Related: 'Novel' swine flu virus sickens Pennsylvania child in 1st case of the year
After being detected in cows in Texas and Kansas, H5N1 infections were also confirmed in cows in Idaho, Michigan and New Mexico, according to the USDA's Animal and Plant Health Inspection Service. As of April 2, the department is also working to test cows in Ohio. (The USDA is regularly updating its website with new information.)
The agency has confirmed that the specific strain of H5N1 infecting cows in additional states appears very similar to the strain found in Texas and Kansas cattle. This strain matches one introduced to the U.S. by wild birds known as clade 2.3.4.4b back in 2021. Before that, the strain had spread mostly in Europe, Asia and Africa.
"[H5N1] could have been infecting dairy cattle a year ago. We just never thought about looking for it," Dr. David Swayne, a bird flu expert who is now a private consultant after having worked for the USDA, told STAT. Experimental data published in 2008 suggested that at least one H5N1 strain can infect baby cows, so it's not totally unexpected to see the virus in cattle.
The recently infected cows have been reported to produce less milk, show poor appetite, develop cold-like symptoms and become lethargic. There have been no reported deaths among the cows.
H5N1 can occasionally infect people and can lead to death, with about 50% to 60% of reported cases resulting in fatal disease. More than 880 human cases of H5N1 have been reported worldwide since the late 1990s, according to the CDC.
Most often, human H5N1 infections occur after a person had close or lengthy unprotected contact without gloves, a face mask or eye protection with infected birds or with objects contaminated with sick birds' saliva, mucus or poop. These cases have not been tied to sustained human-to-human spread of the virus, but there's been some evidence of very limited spread between people.
Although H5N1 infections can be fatal, some people show no symptoms or only mild symptoms. Mild symptoms might include eye infections, such as conjunctivitis (pink eye), and upper respiratory symptoms, like sneezing and coughing. Severe cases can lead to life-threatening pneumonia.
Bird flu can be treated with antiviral drugs used for seasonal flu. The CDC also has several candidate vaccines prepared for manufacturing, just in case this or a closely related virus were to suddenly spread between people; seasonal flu vaccines do not protect against H5N1.
There have been two human cases of H5N1 in the U.S. The first was in 2022, in a person in Colorado who'd had direct exposure to infected poultry. It's possible that this case wasn't a full-blown infection but rather remnants of the virus being detected in the person's nasal passages. The second case was in April 2024, when a person in Texas caught the virus after likely being exposed to infected cows; this person's only reported symptom was pink eye.
Related: 1st-known 'highly pathogenic' bird flu cases in Antarctic could threaten penguins
Finding H5N1 in cows is interesting to scientists because it hasn't been seen before, but as of now, it poses a low risk to the general public.
As for cows, there's some early hints that the virus can spread among cattle the cows in Idaho reportedly became sick after being exposed to cows shipped from Texas, Science reported, and the Michigan cases were also thought to be tied to cows from Texas, the CDC reported. However, H5N1's ability to spread among cows still needs to be confirmed.
In regards to people, "initial testing has not found changes to the [H5N1] virus that would make it more transmissible to humans," the USDA noted in an April statement. "While cases among humans in direct contact with infected animals are possible, this indicates that the current risk to the public remains low."
The CDC also reported that there have been no changes to the virus that would make it less vulnerable to Food and Drug Administration (FDA)-approved antiviral drugs for the flu.
Nevertheless, the CDC recommends that people avoid sick or dead animal carcasses, including wild birds, poultry and cattle. They should also avoid raw milk, poop, litter or other materials contaminated by animals with suspected H5N1 infections, and they should avoid uncooked and undercooked food products from such animals.
The discovery of H5N1 in cows does not threaten the country's milk supply, the USDA noted. Dairies are required to send only milk from healthy animals into processing for human consumption, and the commercial milk supply is pasteurized before going to market, which kills viruses. Unpasteurized milk always carries a risk of causing dangerous infections, but the likelihood of H5N1 infection from raw milk is not yet known.
More information on milk safety given the current situation can be found on the FDA's website.
So far, H5N1 has been found in dairy cows, but the USDA also emphasized that the beef supply is safe and that cooking meat properly kills viruses.
This article is for informational purposes only and is not meant to offer medical advice.
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A person in the United States has tested positive for highly pathogenic avian influenza (HPAI) A(H5N1) virus (H5N1 bird flu), as reported by Texas and confirmed by CDC.
This person had exposure to dairy cattle in Texas presumed to be infected with HPAI A(H5N1) viruses. The patient reported eye redness (consistent with conjunctivitis), as their only symptom, and is recovering.
The patient was told to isolate and is being treated with an antiviral drug for flu. This infection does not change the H5N1 bird flu human health risk assessment for the U.S. general public, which CDC considers to be low. However, people with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at greater risk of infection. CDC has interim recommendations for prevention, monitoring, and public health investigations of HPAI A(H5N1) viruses.
CDC is working with state health departments to continue to monitor workers who may have been in contact with infected or potentially infected birds/animals and test those people who develop symptoms. CDC also has recommendations for clinicians on monitoring, testing, and antiviral treatment for patients with suspected or confirmed avian influenza A virus infections.
This is the second person reported to have tested positive for influenza A(H5N1) viruses in the United States. A previous human case occurred in 2022 in Colorado. Human infections with avian influenza A viruses, including A(H5N1) viruses, are uncommon but have occurred sporadically worldwide. CDC has been monitoring for illness among people exposed to H5 virus-infected birds since outbreaks were first detected in U.S. wild birds and poultry in late 2021. Human illnesses with H5N1 bird flu have ranged from mild (e.g., eye infection, upper respiratory symptoms) to severe illness (e.g., pneumonia) that have resulted in death in other countries.
H5 bird flu is widespread among wild birds in the U.S. and globally. These viruses also have caused outbreaks in commercial and backyard poultry flocks, and sporadic infections in mammals. HPAI in dairy cows was first reported in Texas and Kansas by the U.S. Department of Agriculture (USDA) on March 25, 2024. Unpasteurized milk from sick cattle collected from two dairy farms in Kansas and one in Texas, as well as a throat swab from a cow in another dairy in Texas, tested positive for HPAI A(H5) viruses of the genetic clade 2.3.4.4b, which is the same clade that is widespread among birds globally. On March 29, 2024, USDAs National Veterinary Services Laboratories (NVSL) confirmed HPAI in a Michigan dairy herd that had recently received cows from Texas. The USDA Animal and Plant Health Inspection Service (APHIS) is providing regular updates on detections in dairy herds, as well as information on epidemiological findings and biosecurity guidance for farmers and veterinarians. Preliminary analysis of A(H5N1) viruses has not found changes that would make these viruses resistant to current FDA-approved flu antiviral medications, so these are believed to be effective against these viruses. Candidate vaccine viruses (CVVs) developed against related clade 2.3.4.4b viruses are available for vaccine manufacturing if necessary and preliminary analysis indicates that they may provide reasonable protection against H5N1 influenza viruses. Seasonal flu vaccines do not provide protection against these viruses. Analysis of virus samples is ongoing.
CDC is working closely with state and federal agencies, including USDA, the Food and Drug Administration (FDA), and local health authorities to further investigate and closely monitor this situation.
Prevention Measures
According to CDCs interim recommendations, people should avoid unprotected exposures to sick or dead animals including wild birds, poultry, other domesticated birds, and other wild or domesticated animals (including cattle), as well as with animal carcasses, raw milk, feces (poop), litter, or materials contaminated by birds or other animals with confirmed or suspected HPAI A(H5N1)-virus infection. People should not prepare or eat uncooked or undercooked food or related uncooked food products, such as unpasteurized (raw) milk, or products made from raw milk such as cheeses, from animals with confirmed or suspected HPAI A(H5N1)-virus infection (avian influenza or bird flu). Specific recommendations for farmers; poultry, backyard flock, and livestock owners; and worker protection are also available.
People exposed to birds or other animals with confirmed or suspected HPAI A(H5N1) virus infection should be monitored for any signs and symptoms of illness for 10 days after the last known exposure, including people wearing recommended personal protective equipment (PPE). Additional information on protective actions around birds, including what to do if you find a dead bird, is available on CDCs website.
According to FDA and USDA, there are not concerns with the safety of the commercial milk supply at this time because products are pasteurized before entering the market. Dairies are required to send only milk from healthy animals into processing for human consumption; milk from impacted animals is being diverted or destroyed so that it does not enter the human food supply. In addition, pasteurization has continually proven to inactivate bacteria and viruses, like influenza, in milk. Pasteurization is required for any milk entering interstate commerce for human consumption. FDAs longstanding position is that unpasteurized, raw milk can harbor dangerous microorganisms that can pose serious health risks to consumers, and FDA is reminding consumers of the risks associated with raw milk consumption in light of the HPAI detections.
CDC continues to work with USDA, FDA, and state health departments to monitor people exposed to animals infected with HPAI A(H5N1) viruses. Because influenza viruses constantly change, continued surveillance and preparedness efforts are critical, and CDC is taking measures in case the public health risk assessment changes. This is a developing situation, and CDC will share additional updates as new relevant information becomes available.
Topline
Officials in Texas reported only the second case of avian influenza (bird flu) in a person in the U.S. on Mondayin a patient who had direct contact with infected cattle the infection spreads rapidly among herds across five states, having impacted millions of animals in the land and sea.
Mondays case is the second human case of the H5N1 virus in U.S. history.
The patient was tested by the Centers for Disease Control and Prevention after reporting eye inflammation, according to a news release from the Texas Department of State Health Services, and is recovering while being treated with oseltamivir, an antiviral.
It is the second reported human case of H5N1 in the U.S., after an individual was reported in Colorado in April 2022 who had direct contact with infected poultry.
The new case, which involved direct exposure with suspected infected cattle, does not change the risk for the general public, which remains low, according to TDSHS.
There are no safety concerns about the nations dairy supply as of March 29 because of the pasteurization process required before products hit the market, according to a joint statement from the CDC, U.S. Department of Agriculture and U.S. Food and Drug Administration.
The agencies said in the statement product loss from infected cattle is too limited to have a major impact on supply, adding that it should not have an impact on milk or other dairy product pricesciting the nations seasonally higher production of dairy in spring.
5. Thats how many statesMichigan, Idaho, New Mexico, Kansas and Texashave detected the illness in cattle herds, according to a March 29 joint statement from federal agencies.
There is limited information on the spread of the virus in raw milk, according to federal officials, so the FDA has recommended the dairy industry refrain from manufacturing or selling raw milk or raw/unpasteurized milk cheese products made with milk from cows showing symptoms of illness, including cattle infected or exposed to the virus.
Minnesota reported a case of the virus in a goat on March 20, according to the American Veterinary Medical Association, which marked the first case in a domestic ruminant in the U.S.
Avian flu is typically divided into two categorieshighly pathogenic avian influenza (HPAI) or low pathogenic avian influenza (LPAI)based on its ability to infect poultry, according to the U.S. Geologic Survey. The current outbreak has reportedly affected millions of birds across the globe, and has begun spreading to sea mammalsreportedly killing more than 5,000 sea lions in Peru in 2023which has scientists concerned about the potential risk to human health. Multiple human cases of different strains of the flu have been reported in China and Cambodia. The USDAs dashboard indicates seven flocks of birds in the U.S. have been infected with HPAI in the last 30 days, as of March 20. The cause behind the outbreak in cattle is unknown, the New York Times reported, but federal agencies said transmission between cattle cannot be ruled out. Human cases of the HPAI flu are rare but can occur with prolonged exposure to infected birds, according to the CDC, and there has been no known human-to-human spread of H5N1. There have been only four reported human cases of LPAI in the nations history, according to the CDC, which resulted in mild-to-moderate illness. The virus can present asymptomatically in humans, but common symptoms include conjunctivitis and upper respiratory symptomswhile severe symptoms include fever, shortness of breath and even death.
Bird Flu Found in Michigan, Idaho Cows as Virus Spreads in US (Bloomberg)
Avian flu hits dairy producing cattle farms (ABC News)
First human case of avian flu in Texas raises alarm (Politico)
For the first time, U.S. dairy cows have tested positive for bird flu (NPR)
Bird flu case confirmed in Texas in person who had exposure to dairy cattle Livestock in Texas, Kansas and Michigan are confirmed to have the virus, and herds in New Mexico and Idaho have also tested positive. Officials confirmed that one person in Texas also had bird flu.
Dairy cattle feed at a farm on March 31, 2017, near Vado, N.M. The U.S. Department of Agriculture says cows in multiple states have tested positive for bird flu. Rodrigo Abd/AP hide caption
Dairy cattle feed at a farm on March 31, 2017, near Vado, N.M. The U.S. Department of Agriculture says cows in multiple states have tested positive for bird flu.
Livestock at multiple dairy farms across the U.S. have tested positive for bird flu also known as highly pathogenic avian influenza, or HPAI in an outbreak that's likely spread to at least five states.
The U.S. Department of Agriculture's Animal and Plant Health Inspection Service confirmed Friday that cows in Texas, Kansas and Michigan had been sickened by the virus, and there were presumptive positive test results for additional herds in New Mexico and Idaho.
It's the first time the disease has been found in dairy cattle, according to the American Veterinary Medical Association.
On Monday, the Texas Department of State Health Services announced that a person who was exposed to dairy cattle presumed to be infected with bird flu had also caught the virus.
It is only the second time a human in the U.S. has contracted HPAI A, or H5N1, according to the Centers for Disease Control and Prevention. A person in contact with infected poultry was sickened in Colorado in 2022.
Texas issued a public health alert Monday, asking health care providers in the state to be on the lookout for people with symptoms of bird flu who may have been exposed to an infected person or animal.
The new cases come just days after a group of young goats contracted bird flu on a Minnesota farm.
Bird flu infects the respiratory and gastrointestinal tracts of birds and is often fatal to avian populations. It can spread from wild birds to commercial poultry and backyard flocks as well as terrestrial and marine mammals and humans.
Government officials say the risk to the public amid the current outbreak remains low. Most past human infections have occurred after people had "unprotected exposures to sick or dead infected poultry," according to the CDC, and it's rare for a human to transmit the disease to another person.
Officials say the strain of the virus detected in Michigan is similar to the one found in Texas and Kansas, which was shown through initial testing not to include any changes that would make it more transmissible to humans.
The rash of bird flu infections should also not dramatically impact consumers of dairy products, federal and state officials say.
"The good news is this is not a serious problem," Texas Agriculture Commissioner Sid Miller told NPR on Sunday. "It's not going to bankrupt anybody. Cows basically have the flu for a week, and they get over it."
The country's commercial dairy supply is safe and a milk recall is unnecessary, the USDA says.
That's because dairies are required to divert or destroy any milk from impacted livestock, and only milk from healthy cows can be processed for human consumption.
Additionally, pasteurization which is required for milk entering interstate commerce kills bacteria and viruses, including influenza.
The Food and Drug Administration says there is limited information available about the transmission of bird flu in raw, unpasteurized milk. The agency has long warned people to avoid raw milk, which it says can harbor dangerous bacteria and sicken consumers.
Federal officials say the loss of milk from ill dairy cows is too limited to significantly impact the commercial supply, which is typically higher in the spring due to increased seasonal production. Dairy prices are not expected to rise due to the outbreak, they added.
The USDA believes the dairy cows have been sickened by a strain called H5N1, Eurasian lineage goose/Guangdong clade 2.3.4.4b, which was likely introduced by wild birds. Pigeons, blackbirds and grackles were identified at the affected Texas farms.
But federal officials are also not ruling out the possibility of cow-to-cow transmission. That's after a Michigan farm recently received a shipment of cattle from an affected Texas farm before any of the cows show signs of disease, the Michigan Department of Agriculture and Rural Development said Friday.
While there are still many unknowns, the available evidence collected from infected cattle isn't alarming to Richard Webby, a virologist from Saint Jude Children's Research Hospital in Memphis, Tennessee.
"There's nothing in the sequence of the virus that sort of immediately screams that it has changed, and that's why these cows are getting infected," he said. "It just seems to be fairly typical of the viruses that have been detected in birds in various regions."
Cows sickened by bird flu at affected dairy farms have recovered "after isolation with little to no associated mortality reported," according to the USDA.
Texas officials said Monday that the person who tested positive for bird flu had reported eye inflammation, or conjunctivitis, as their only symptom. They were told to isolate and were being treated with oseltamivir, an antiviral drug.
Federal and state agencies are continuing to test sick livestock and unpasteurized milk samples.
The USDA also recommends that farmers and their veterinarians practice "good biosecurity," which includes limiting animal movements, testing livestock before they're moved and isolating sick cows.
NPR's Will Stone contributed reporting.
Bird flu is always a concern for health officials, not only for its effects on food supply chains, but for its potential for causing infections in humans. However, rarely, if ever, do humans contract this virus.
But the Texas Department of State Health Services reported on April 1 that a person contracted H5N1, a strain of bird flu.
The agency indicated the persons only symptom is eye inflammation. The person was infected by cattle, a development that could be a cause for concern, according to Sam Scarpino, a public health expert and professor at Northeastern University.
Bird flu has been around for basically as long as weve been thinking about human flu, Scarpino says. Its a pretty persistent problem because its always spilling over into mammals, including humans. It affects domestic bird population, poultry, et cetera. Its something that were persistently worried about causing another pandemic, and were paying attention to it a lot.
The types of flu found in birds often dont make their way to humans. These flus primarily infect birds gastrointestinal system, which means the cell receptors for the virus are in the gut of the bird. The same cell receptors can be found in humans lower respiratory tract.
That means its harder to get infected because the virus has to get in deeper, past more of the innate immune system, Scarpino said. But lower respiratory infections are bad and you also then are infected with something that youre totally naive too and your immune system goes haywire.
These infections also can range from mild to severe with high fatality rates. However, given the way the virus travels, it usually doesnt transmit from birds to humans.
Basically every modern influenza pandemic going back to 1918 and probably pre-1918 had at its origin of bird flu, Scarpino said. However, that bird flu will have almost certainly spent time in some intermediate host before it caused a human pandemic.
In this case, the virus was found in cattle that likely served as an intermediary host. The specific variant, H5N1, is one found more often than humans.
This bird flu has also moved from sea birds to seals and sea lions, killing thousands across the globe.
The jump between species, along with risk to humans posed by this particular strain, is why public health officials are watching the situation, Scarpino said.
The reason that were having this conversation is because everybodys worried about the chance of a pandemic that could be sparked by the transition from a bird flu into a human flu, Scarpino said. The level of concern in terms of human health is low. (But) the concern that I have is everything happening right now is pretty unprecedented.
Historically, there have not been a lot of bird flu cases in cattle up until now, Scarpino said. This case could be a fluke and the result of some shifts in cattle movement this year.
Whether the infection is something likely to spread to humans depends on what caused it to spread to cattle and what happens if the cows are spreading it to each other.
Scarpino said the fact the person with the flu only has eye symptoms is promising because it shows the virus may not be readily transmissible. But Scarpino said public health officials need to determine if how and why its spreading to cattle in order to assess the risk to people.
Its possible its just bad luck, he said. Its totally possible that something unusual happened in Texas. The problem is I havent seen a really compelling explanation for whats going on aside from it was just bad luck. Sort of hoping something was bad luck is not great public health policy. Were sort of assuming the cows are more like horses which means theyre a bit more susceptible to bird flu and so its not a big risk but Id love to have that assumption tested.
Scarpino said pasteurization prevents the virus from infecting milk products. However, the infections could cause a dip in supply that could lead to an increase in prices.
If we look at it in terms of the food supply supply, we talked about how theres massive culling of poultry to prevent this, said Darin Detwiler, an associate teaching professor of food policy and food safety expert at Northeastern University. This causes disruption within our supply systems, results in economic losses within the industry and consumers end up paying more for these products.
Ditwiler said there could also be a ban on food products from certain areas where bird flu has spread.
But overall, he said, the average person doesnt have reason to be too worried about bird flu yet.
If youre not interacting with animals, you dont need to necessarily be concerned, Ditwiler added. As always, I think consumers should make educated decisions and always buy food from trusted sources. Dont buy meat from some guys pickup truck on the county highway down by the river. Now is not the time.
