Welcome to The Topline, a weekly roundup of the big numbers driving the Minnesota news cycle, as well as the smaller ones that you might have missed. This week: bird flu in milk; soil erosion; expensive cigarettes; longevity; and visits to Minneapolis.
A veterinary epidemiologist at Ohio State University collected 150 milk products from store shelves in multiple states across the Midwest, STAT News reports, and tested them for DNA from the H5N1 bird flu virus. Fifty-eight of the samples came back positive.
The viral DNA was almost certainly inactive, likely killed off by pasteurization. Tests are underway to verify that now. But the initiative underscores that bird flu is almost certainly more widespread among dairy herds than previously thought, and spreading in potentially unpredictable ways.
Scientists in Texas, for instance, have documented five H5N1 deaths among cats on two dairy farms, either from drinking unpasteurized milk or eating birds infected with the disease.
Some experts are worried the federal government is making the same mistakes it did in the early days of the COVID-19 pandemic, with sluggish testing and a lack of urgency. So far only two humans have come down with the flu in the U.S., according to the Centers for Disease Control and Prevention. Theyve suffered only mild symptoms, and the agency says the virus doesnt spread readily between people.
But viruses are capable of changing over time, and an unchecked pandemic raging among birds and now cattle gives H5N1 a lot of chances to roll the genetic dice and potentially turn up a mutation thats more threatening to people.
The National Weather Service Grand Forks recently shared this video of thick clouds of topsoil blowing across roadways near the city and creating hazardous driving conditions. It happens all across the Midwest this time of year: Strong dry winds blow huge quantities of soil off traditionally tilled fields, while rains wash away additional amounts.
U.S. farms are currently losing twice as much topsoil to erosion per year as the Great Plains lost in a typical year at the height of the 1930s Dust Bowl, the Union of Concerned Scientists noted in 2020. The average American crop farm loses about 2 tons of soil from every acre to wind every year, and another 2.7 tons to water, the group estimates.
All that soil is laden with pesticides, fertilizers and other chemicals that foul the countrys waterways and pollute the air, and its expensive to farmers to replenish the treatments that they lose to erosion.
Last week the Minneapolis City Council unanimously adopted an ordinance raising the minimum price of cigarettes to $15 a pack, which is likely the highest price in the nation, MPR News reports. In pricey New York City, for instance, a pack of smokes will set you back only $13.
Cigarettes are highly addictive and cause a panoply of horrible health conditions, including cancer, heart disease, stroke, lung diseases, diabetes, and chronic obstructive pulmonary disease, according to the CDC. They cause about half a million deaths each year, and cut short the lives of the people who use them by an average of 10 years.
Research has consistently shown that simply raising their prices is the best way to reduce consumption.
Smoking features prominently in the next finding, which comes from a National Bureau of Economic Research paper released last week: People who live in areas with larger proportions of college graduates live longer, healthier lives, regardless of how much education theyve individually received.
The researchers attribute this primarily to social spillover effects on obesity and smoking rates. Smoking, in particular, is more stigmatized in highly educated areas, and people living in those areas are more likely to work in smoke-free workplaces.
The correlation has gotten stronger over time, and is especially strong for rural and Hispanic people.
Despite seemingly half of Minnesota vowing never to set foot there, Minneapolis saw the biggest increase in downtown visitors over the past year out of any North American city, wrote Bring Me The News in a fantastic tweet highlighting this finding.
The data comes from a cell phone study by researchers at the University of Toronto who found that foot traffic to Minneapolis increased by 45% from March 2023 to February 2024. Big events, like Taylor Swift concerts and the Pride Festival, are likely driving some of this.
Fragments of the virus that causes bird flu, H5N1, were found in roughly1 in 5 pasteurized milk samplesacross the US, the Food and Drug Administration announced Thursday. A day later, the agency posted an update with good news, confirming that additional testing of the samples didn't turn up active or infectious virus. That's what experts have said would be the case, since pasteurization is expected to kill or inactivate bird flu virus, as it does other potentially harmful bacteria and viruses.
The FDA says the milk supply remains safe; pasteurization is a requirement for commercial milk, making up the vast majority of milk found on store shelves -- thoughnot all, depending on local lawsaround raw milk sales.
Still, the evidence of virus in pasteurized milk was jarring. Since bird flu was first reported in US dairy cows, evidence of it had only previously been reported in unpasteurized, raw milk, which hasn't gone through the heating process to get rid of viruses and bacteria like pasteurized products have. It suggests the virus has been spreading more widely than what's been realized in cattle.
This has prompted some scientistsandinfectious disease expertsto express concerns about US health agencies' response to bird flu in farm animals and the lack of information provided around samples, despite the current health risk to people remaining low. Virologist Angela Rasmussen, for example,said in an X threadlast week that the new milk sample findings suggest the disease may be spreading asymptomatically in cows, more broadly than previously thought and that an "apparent lack of transparency and urgency" to share relevant data may be harming the ability to respond.
And what about the noncommercial milk supply, or raw milk that hasn't been pasteurized? While people who grew up on farms or around cattle might have had unpasteurized milk for dinner, raw milk has found a growing audience: people seeking it out for wellness purposes or sometimes traveling to local farms to consume a food they feel is more natural or holistic.
About raw milk or dairy products during these bird-flu times, citing limited information on bird flu in dairy, the FDA says it doesn't know whether bird flu viruses can be transmitted through unpasteurized products. The agency is reiterating its generalstance that people should avoid consuming raw or unpasteurized milk.
The experts I spoke with for this story before it was first published earlier this month essentially said, in general, influenza isn't spread to people through eating or drinking. However, they stressed the existing health risks of raw milk, which isn't part of what the FDA refers to as the "commercial" milk supply.
"In my opinion, there's a concern with raw milk acquisitions which can become part of the food system, and people secure that milk outside of going to the grocery store," Meg Schaeffer, an infectious disease epidemiologist and National Public Health adviser at the analytics firm SAS, told CNET before this article was first published.
On Monday, she followed up in a separate conversation to say that more information on raw milk and bird flu may come in the coming weeks, citing the one human case of bird flu that's been linked to contact with an infected dairy cow. The person's only symptom was conjunctivitis (pink eye), which presumably came from infected milk that somehow got into their eye, according to Schaeffer.
"There's two parts to the warning," Schaeffer said of the FDA's notice. "The first is that they do believe the pasteurized milk supply is safe and all of the evidence that we have to date points to that." The second is that you shouldn't drink raw milk -- in general, but especially now.
"Yes, we have enzymes in our body that can kill the virus," she said. "It's not a likely pathway to infection, but it's not impossible."
Here's what to know about pasteurization in milk and how to consider the raw milk wellness trend in bird flu times.
Pasteurization is a heating process invented in the 1860s by French chemist Louis Pasteur and has been used widely since as a means to kill harmful bacteria and pathogens that can sometimes cause serious illness. These include bacteria that cause illness like E. coli, Listeria and Salmonella, and other pathogens.
Pasteurization is also expected to kill or inactivate the virus that causes bird flu, which is why health officials continue to say there's no risk to pasteurized dairy products or the commercial milk supply.
Some dairy products may be ultrapasteurized, which is when milk is heated more quickly than typical pasteurization (a couple of seconds) at a higher temperature and then rapidly cooled down. This extends its shelf life.
Pasteurized dairy products can be organic or nonorganic. Whether you can buy or sell raw, unpasteurized milk depends on the laws in your state. In California, for example, you can buy raw milk from stores, although it has to be properly labeled with a warning stating it's unpasteurized.
Jenna Guthmiller, an immunologist, influenza researcher and assistant professor in the Department of Immunology and Microbiology at the University of Colorado, told CNET for the article's first publish that if someone were to drink milk contaminated with H5N1, it doesn't necessarily mean they would be infected. Influenza viruses are unstable outside the body, she explained, and milk "bypasses the normal process by which we get infected" with flu.
Dr. Amesh Adalja, an infectious disease specialist and senior scholar at the Johns Hopkins Center for Health Security, said in an email last week that finding bird flu virus material in pasteurized milk doesn't change the public health risk assessment for the commercial milk supply.
"Pasteurization is a process that would destroy the viability of pathogens -- it's not a process that eliminates their genetic material," he said.
Adalja previously noted it's "unclear" whether there would be a live virus in unpasteurized milk or if it could infect humans by their drinking it, he explained. Influenza viruses aren't spread to humans via ingestion. But on raw milk, he added, "there are many reasons not to drink it to begin with."
While theFDA saysthat it doesn't know yet whether bird flu can transmit to people via unpasteurized or raw dairy, it's probably not a reach to assume that raw milk is a riskier choice avian-influenza-wise than commercial milk, since raw milk hasn't gone through any type of process that would inactivate viruses.
In general, drinking raw milk has health risks. In addition to what Guthmiller called "old timey" bacteria that used to be a problem back in the day, before processes like pasteurization cleaned up the food supply, unpasteurized or raw milk can expose people to serious illnesses like E. coli and listeria. While it may cause only temporary or milder illness in most people, people with weakened immune systems, older adults, those who are pregnant and very young children are especially at risk of serious health effects from drinking unpasteurized milk.
The risk is especially high in children, according to Schaeffer, who are vulnerable to severe illness. In serious cases, health effects from drinking raw milk that's been contaminated can lead to kidney failure.
Schaeffer also pushed back on claims that diseases that once were a big problem in countries like the US, like tuberculosis, are no longer an issue. That's true about tuberculosis, she said, but we also have effective treatment for it. That's not the case, she said, for some types of illness that children can get from unpasteurized milk.
"The diseases, if anything, are even stronger -- antibiotic resistant," Schaeffer said. She added that some bacteria that may be in raw milk may go undetected by farmers because they don't cause illness in cows but do in people.
While buying raw milk from a farm you know sets higher safety standards and practices "good hygiene" during milking can reduce the risk of contaminated raw milk,it won't eliminate it, according to the CDC.
Proponents of raw or unpasteurized milk prefer it fordifferent reasons, including its creamier texture and taste or anecdotal reports that it's easier on digestion or more nutritious.
You can't argue with someone's taste or texture preferences when it comes to food. In terms of the nutritional or health benefits of raw milk compared with unpasteurized milk, research seems to have pushed back on or debunked the majority of claims. The FDA, for example, says thatraw milk isn't a cureor antidote for lactose intolerance. The agency also claims on the same informationpagethat people are misusing the results of a study from 2007 that was on farm milk consumption, not raw milk consumption.
In an analysis of the risks versus benefits of raw milk research,Healthlinereported that any small antimicrobial benefit from raw milk would be neutralized when it's refrigerated. It also reported, based on the results of asystematic review, that minor nutrient losses of water-soluble vitamins, including some B vitamins, are already low in milk generally.
"Multiple studies have shown that pasteurization does not significantly affect the nutritional quality of milk," theCenters for Disease Control and Prevention concludes. "Scientists do not have any evidence that shows a nutritional benefit from drinking raw milk."
As someone who grew up on a dairy farm, Guthmiller used to drink unpasteurized milk herself -- she gets it. When it comes to consuming raw milk, she said, "the risks certainly outweigh the pros."
"We're getting to a point with pasteurization where it looks like real milk," Guthmiller said. In terms of nutritional quality, "you really do not affect the contents of the milk" by pasteurizing it, she said, because it's done so quickly.
If you're looking for foods with provengut-health properties, look at adding foods like kimchi, pickled vegetables, sourdough,apple cider vinegarand buttermilk.
I'd be a hypocrite if I wrote this without noting I've experimented with a few things in the wellness realm that were either not recommended by a health body like the CDC, or "rooted in science," as they say. Sometimes, I like wading into wellness waters tipped toward murky in the swirl of potential risk with potential benefit. A couple of tamer or lower-risk, lower-evidence examples include a time in my life when I dumped a spoonful ofcoconut oil into my coffeeeach day and the fact that I own a pair ofblue-light-blocking glasses.
Prior to bird flu in dairy cow times, theideaof raw milk was also intriguing to me because I like the notion of prioritizing foods that are locally sourced and full of fat for their satiating properties. But you won't find me traveling upstate to a local farm for a fresh jug of raw milk. This is true even as my current individual risk is relatively lower than that of a child or someone who's pregnant, and even if the milk supply remains safe, and bird flu proves virtually impossible to transmit through milk. (Outside of milk, it's worth noting thatanimal-to-human transmission of virusesis a growing threat.) I can get the same small or hypothetical benefit from other whole food sources outside raw milk, without rolling the public health dice.
Avian influenza has been tearing through poultry, wild birds and even mammals without seriously affecting many people in the current outbreak. But in recent weeks, the virus has begun infecting U.S. dairy cows: the Centers for Disease Control and Prevention has reported sick animals in at least 34 herds as of April 26. And a human case involving a dairy worker in Texas has ramped up concerns that the virus, known as H5N1, could spread more widely in people. The U.S. Department of Agriculture has announced it will test ground beef in states with outbreaks as a precaution, although the virus is thought to spread through close contact with infected animals.
With COVIDs rapid development into a lethal pandemic still fresh in many peoples mind, its difficult to know how worried we should be about another infectious respiratory disease gaining ground. So Scientific American spoke with Katelyn Jetelina, an independent epidemiologist who writes a popular public health newsletter, about how the outbreak has gone so far and how the U.S. could strengthen its managementwhich she says began as a very uncoordinated, messy response.
[An edited transcript of the interview follows.]
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As an epidemiologist who followed COVID closely, what has it been like for you to watch the bird flu situation unfold?
Theres been a lot going on and pretty quickly, which I think is making us epidemiologists and virologists, as well as veterinarians, a bit nervous. H5N1 has been really heating up in the past two or three years, but what makes the past couple of months unique is that this is spreading among cows.
The mantra we always work on is that spillovers are common, but pandemics are rare because so many unlucky things have to happen in sequence. But pandemics are a game of roulette: they rely on luck, and they can get dramatic pretty fast.
Are we repeating the mistakes of the early days of COVID?
There are things weve learned and things we havent learned. One of the biggest challenges with this is: it involves humans and animals, so there are a lot of playerswe have multiple agencies working in their lane. Ive been impressed with how the CDC has been updating the public, and I hope thats because they learned their lesson during COVID. Other players havent necessarily learned those lessons because they werent in the COVID trenches.
One key difference [with bird flu] is: this hasnt seen human-to-human spread. Were not talking about January through March 2020. I do think that we are watching this unfold in real time better than we did with COVID, which seemed to be coming out of nowhere, so that gives me a little more hope.
How have scientists been tracking the spread of bird flu in cows?
We dont have a good sense of the spread because testing is voluntary and certainly not being done in a systematic way. Were pretty much flying blind with the testing aspect.
But we have had two clues that this virus has spread very widely: The Food and Drug Administration found viral fragments in milk. And genomic surveillance estimates that spillover to dairy cows started back in December 2023, if not earlier, which means this has been spreading under our noses for a much longer time than we originally thought.
That means our surveillance systems are not great. It also means we havent been testing enough. We dont think that this means the virus is being spread to humans, but it may mean that H5N1 is starting to find a new host in cows, which would not be great news.
Should people be worried about getting the H5N1 virus from milk?
It sounds scary, and I understand the concern. One thing that has made me calm down is knowing that weve had, like, 100 years of data around pasteurization, and it works really well. We also got confirmation that scientists were not able to grow active virus from the milk samples, which were pasteurized. That means these virus fragments detected in milk were broken pieces that cannot replicate and thus cannot harm humans. This is a good sign.
Do we know how the virus jumped into cows or how its spreading?
From the genomic surveillance, it looks like the spread to cows was likely from one sourceprobably a dead bird. One hypothesis is that the virus got into cow feed, and then cows ate it, and then it started spreading from cow to cow through the milk machines. But a lot of this is still up in the air.
Veterinarians swabbing cows have found the most virus in the udders, but they have found other positive swabs from, for example, lung tissue. So how is this actually spreading? We think its the milk machines spreading the virus from cow to cow, but we need to make sure that its not via respiratory transmission as well.
A huge new puzzle is that there is also transmission from cows to poultry. That is concerning; it gives this virus even more opportunity to adapt because it keeps jumping from species to species, and we dont know how. Is it through humans? Is it through rats? Is it through feed? We don't know. Trying to get a really good understanding of epidemiology here has been challenging just because the data are limited, and the communication is suboptimal.
The CDC says there has only been one case in humans from this outbreak. How plausible is that?
Im a little skeptical because we havent been doing asymptomatic testing, and symptomatic testing is voluntary. There have been reports this week that there are other humans who had symptoms who didnt test.
Until we start seeing data, I dont think we should come to sweeping conclusions that its only one human case. The good news is that it doesnt seem like anyones died yet, and were not seeing huge clusters [of sick people] in emergency departments. So if there are more human cases, Im pretty confident theyre from direct contact with cows rather than human-to-human transmission. But we need more data and more communication around this.
Many people who have close contact with cows are migrant workers, some of whom are likely undocumented. Does that make them less likely to report any flu symptoms?
Yeah, there are so many layers to this. If they test positive, theyre not going to be able to work, and that has huge implications for their family. The other two big challenges that the CDC brought up publicly are that theres a language barrier and that some of these people are undocumented workers with a lack of trust in government institutions.
Are we monitoring the virus in wastewater like we did for the virus that causes COVID?
One huge lesson we learned during the COVID pandemic is the value of wastewater. This is a perfect case to leverage this massive network that we built to try and figure out how and where H5N1 is spreading, given the limitations and biases of testing right now. Whats been disappointing is that the government has not officially shared any [flu data from] wastewater. To monitor human infections, the CDC said that theyre utilizing emergency department data, which is great. But once an outbreak hits emergency departments among humans, its already kind of out of control, so I would love to see wastewater surveillance leveraged a whole lot more.
If we need vaccines and treatments for bird flu, how prepared are we?
The government has confirmed that tools such as Tamiflu [an antiviral medication] would work to a certain extent against H5N1. Of course, Tamiflu is not very effective even against our seasonal flu. We also have stockpiled H5N1 vaccines that are predicted to have efficacy if this does move to humans, which is great news. [Editors Note: These vaccines require two doses per person. The U.S. government says it has some 10 million doses available and could make about 125 million or so within four months, which would total enough to cover about one fifth of the country.]
But there are still a lot of unanswered questions: What about manufacturing and supply? What about the rest of the globe? What about vaccine hesitancy and declining trust and access problems? Fully relying on vaccines and overconfidence were some of the biggest mistakes of the COVID emergency, and I think its best to face these threats and questions with a level of humility and determination.
When should people who work with livestock get access to those vaccines?
I dont know what that line is, when were like, This is an oh, shit moment versus a watch and see moment. Getting that line incorrect has massive implications. Certainly if we start seeing any trace of human-to-human transmission, we would really need to start ramping up. If we start seeing transmission in pigs, that would make me incredibly nervous. Pigs are a really great mixing vessel for influenza, so it would be incredibly easy for this virus to start mutating in a way that would have implications for humans. Veterinarians are continuing to test pigs for H5N1, and they have so far been negative, so Im really happy were on top of that.
Whats missing from the U.S.s H5N1 response right now?
We need a coordinated response from our government. I get that there are multiple players who have their own priorities and legal authorities, but honest, frequent, direct communication earns the publics trust and confidence. When communities are starved for good information during outbreaks, it leads to unnecessary anxiety, confusion and frustration. The winds may be changing in this area, but we need to get better faster.
On the ground, we really need to get a handle on where H5N1 is spreading and how. That comes through asymptomatic testing of animals and people, sharing genomic surveillance data with the global community and understanding wastewater trends. So certainly, a lot more work needs to be done.
How worried should people be right now?
This is not a concern for the average American unless theyre working with a livestock. What I tell my mom, for example, is that the general public doesnt have to worry. This is very low-risk to them at the moment. But that could change.
I think the most we can do is to know that this is going on and to pay attention to the status of the situation by finding trusted sources of information. There is so much misinformation and disinformation that finding and sticking to those credible sources is going to be incredibly important if this situation continues to evolve, which we expect it to.
Topline
There has been a global outbreak of H5N1 bird flu since 2020, but recent outbreaks among cattle in several U.S. states has experts concerned the virus may mutate and eventually spread to humans, where it has proven rare but deadlyand the USDA has begun testing ground beef in grocery stores.
A sign warns of a outbreak of bird flu.
The global H5N1 bird flu outbreak began in 2020 after a reemergence in birds in Europe and led to the deaths of millions of birds, but its evolved and has increasingly been infecting mammals (on land and sea), which means it could possibly spread to humans, according Jeremy Farrar, chief scientist for the World Health Organization.
A wider variety of mammals are dying from bird flu, which also has experts concerned it may mutate to more easily infect humans: the first report of a walrus dying from bird flu was detected Monday on one of Norways Arctic Islands, and the first U.S. dolphin infected with bird flu died back in 2022, according to a report published Friday.
As of April 26, more than 90 million poultry (primarily chickens) in 48 states have been euthanized because of bird flu since 2022, and 34 dairy cow herds across nine states have tested positive, according to data from the Centers for Disease Control and Prevention (unlike chickens, cows appear to recover from the virus).
The Department of Agriculture first detected bird flu in dairy cows in March, and it believes the cows fell ill after coming into contact with infected birds, though it confirmed in an update from last week that cow-to-cow transmission through infected unpasteurized milk may also be a factor.
One in five milk samples gathered from grocery stores across the country tested positive for dead remnants of bird fluresults were higher in areas with cow outbreaksthough the Food and Drug Administration advises these remnants dont pose a threat and pasteurized milk is still safe to drink because the pasteurization process kills the live virus.
However, the FDA warned against consuming raw milk, which has caused some experts to call for a ban against selling raw milk because it could seriously sicken people; the interstate sale of raw milk is illegal, but some states like Texas, Idaho and New Mexicowhich all have bird flu outbreaks among dairy cowsallow it.
The USDA told Forbes Monday it will begin testing ground beef samples from grocery stores in states with cow outbreaks, and test ground beef cooked at different temperatures and infected with the virus to determine if it's safe to eat.
Because the virus is commonly spread through the movement of migratory birds, certainly there is a risk for cows in other countries to be getting infected," Wenqing Zhang, head of WHO's Global Influenza Programme, said at a news briefing Tuesday.
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Bird flu doesnt transmit easily from person-to-person, according to the World Health Organization. Bird flu rarely affects humans, and most previous cases came from close contact with infected poultry, according to the CDC. Because human-to-human spread of bird flu poses pandemic potential, each human case is investigated to rule out this type of infection. Though none have been confirmed, there are a few global casesnone in the U.S.where human-to-human transmission of bird flu was thought to be probable, including in China, Thailand, Indonesia and Pakistan.
It is very deadly. Between January 2003 and March 28, 2024 there have been 888 human cases of bird flu infection in humans, according to a report by the World Health Organization. Of those 888 cases, 463 (52%) died. To date, only two people in the U.S. have contracted H5N1 bird flu, and they both were infected after coming into contact with sick animals. The most recent case was a dairy worker in Texas who became ill in March after interacting with sick dairy cows, though he only experienced pink eye. The first incident happened in 2022 when a person in Colorado contracted the disease from infected poultry, and fully recovered.
Raw, unpasteurized milk is unsafe to drink, but pasteurized milk is fine, according to the FDA. Bird flu has been detected in both unpasteurized and pasteurized milk, but the FDA recommends manufacturers against making and selling unpasteurized milk since theres a possibility consuming it may cause bird flu infection. However, the virus remnants in pasteurized milk have been deactivated by the heat during the pasteurization process, so this type of milk is still believed safe to consume.
The CDC warns against eating raw meat or eggs infected with bird flu because of the possibility of transmission. However, no human has ever been infected with bird flu from eating properly prepared and cooked meat, according to the agency. The possibility of infected meat entering the food supply is extremely low due to rigorous inspection, so properly handled and cooked meat is safe to eat, according to the USDA. To know when meat is properly cooked, whole beef cuts must be cooked to an internal temperature of 145 degrees Fahrenheit, ground meat must be 160 degrees and poultry must be cooked to 165 degrees. Rare and medium rare steaks fall below this temperature. Properly cooked eggs with an internal temperature of 165 degrees fahrenheit kills bacteria and viruses including bird flu, according to the CDC. It doesnt matter if they may or may not have [avian]
Symptoms of bird flu include a fever, cough, headache, chills, shortness of breath or difficulty breathing, runny nose, congestion, sore throat, nausea or vomiting, diarrhea, pink eye, muscle aches and headache. However, the CDC advises it cant be diagnosed based on symptoms alone, and laboratory testing is needed. This typically includes swabbing the nose or throat (the upper respiratory tract), or the lower respiratory tract for critically ill patients.
This years egg prices have increased as production decreased due to bird flu outbreaks among poultry, according to the USDA. A dozen large, grade A eggs in the U.S. costed around $2.99 in March, up almost a dollar from the fall. However, this price is down from a record $4.82 in January 2023, which was also spiked by bird flu outbreaks. Earlier this month, Cal-Maine Foodsthe countrys largest egg producertemporarily halted egg production after over one million egg-laying hens and chickens were killed after being infected with bird flu.
Once chickens have been infected with bird flu, farmers quickly kill them to help control the spread of the virus, since bird flu is highly contagious and fatal in poultry. The USDA pays farmers for all birds and eggs that have to be killed because of bird flu, as an incentive to responsibly try and curb the spread of the disease. The USDA has spent over $1 billion in bird flu compensation for farmers since 2022, according to the nonprofit Food & Environment Reporting Network.
The FDA has approved a few bird flu vaccines for humans. The U.S. has a stockpile of vaccines for H5N1 bird flu, but it wouldnt be enough to vaccinate all Americans if an outbreak were to happen among humans. If a human outbreak does occur, the government plans to mass produce vaccines, which can take at least six months to make enough for the entire population. Sequirs, the maker of one of the approved vaccines, expects to have 150 million vaccines ready within six months of an announcement of a human bird flu pandemic. Although there are approved vaccines for other variants designed for birds, there are none for the H5N1 variant circulating. However, the USDA began trials on H5N1 animal-specific vaccines in 2023.
The virus spreading in cattle recently has experts concerned it may mutate and spread more easily in humans, though the CDC said its risk to the public remains low. Farrar called the cattle infections in the U.S. a huge concern, urging public health officials to continue closely monitoring the situation because it may evolve into transmitting in different ways. The increased number of mammal bird flu infections since 2022 could indicate that the virus is looking for new hosts, and of course, moving closer to people, Andrea Garcia, vice president of science, medicine and public health for the American Medical Association, said. More than 10 human bird flu cases were reported to the World Health Organization in 2023, and all but one survived. Bird flu has devastated bird populations, and 67 countries reported the deaths of 131 million poultry in 2022 alone. Although bird flu typically infects wild birds and poultry, its spread to other animals during the outbreak, and at least 10 countries have reported outbreaks in mammals since 2022. Around 17,400 elephant seal pups died from bird flu in Argentina in 2023, and at least 24,000 sea lions died in South America the same year. Besides cattle, bird flu has been detected in over 200 other mammalslike seals, raccoons and bearsin the U.S. since 2022. Although rare, even domestic pets like dogs and cats are susceptible to the virus, and the FDA warns against giving unpasteurized milk to cats to avoid possible transmission.
WHO Warns Threat Of Bird Flu Spreading To Humans Is Great Concern (Forbes)
One In Five Milk Samples From Across US Had Traces Of Bird Flu Virus, FDA Says (Forbes)
Can Pets Get Bird Flu? Heres What To Know (Forbes)
Avian H5N1 (Bird) Flu: Why Experts Are WorriedAnd What You Should Know (Forbes)
The ongoing outbreak of H5N1 avian flu virus looks a lot like a public-health problem that the United States should be well prepared for.
Although this version of flu is relatively new to the world, scientists have been tracking H5N1 for almost 30 years. Researchers know the basics of how flu spreads and who tends to be most at risk. They have experience with other flus that have jumped into us from animals. The U.S. also has antivirals and vaccines that should have at least some efficacy against this pathogen. And scientists have had the advantage of watching this particular variant of the virus spread and evolve in an assortment of animalsincluding, most recently, dairy cattle in the United Stateswithout it transmitting in earnest among us. Its almost like having the opportunity to catch COVID-19 in the fall of 2019, Nahid Bhadelia, the founding director of Boston University Center on Emerging Infectious Diseases, told me.
Yet the U.S. is struggling to mount an appropriate response. Because of the coronavirus pandemic, the nations alertness to infectious disease remains high. But both federal action and public attention are focusing on the wrong aspects of avian flu and other pressing infectious dangers, including outbreaks of measles within U.S. borders and epidemics of mosquito-borne pathogens abroad. To be fair, the United States (much like the rest of the world) was not terribly good at gauging such threats before COVID, but now we have had our reactions thrown completely out of whack, Bill Hanage, an infectious-disease epidemiologist and a co-director of the Center for Communicable Disease Dynamics at Harvards School of Public Health, told me. Despite all that COVID put us throughperhaps because of itour infectious-disease barometer is broken.
H5N1 is undoubtedly concerning: No version of this virus has ever before spread this rampantly across this many mammal species, or so thoroughly infiltrated American livestock, Jeanne Marrazzo, the director of the National Institute of Allergy and Infectious Diseases, told me. But she and other experts maintain that the likelihood of H5N1 becoming our next pandemic remains quite low. No evidence currently suggests that the virus can spread efficiently between people, and it would still likely have to accumulate several more mutations to do so.
Thats been a difficult message for the public to internalizeespecially with the continued detection of fragments of viral genetic material in milk. Every expert I asked maintained that pasteurized dairy productswhich undergo a heat-treatment process designed to destroy a wide range of pathogensare very unlikely to pose imminent infectious threat. Yet the fear that dairy could sicken the nation simply wont die. When I see people talking about milk, milk, milk, I think maybe weve lost the plot a little bit, Anne Sosin, a public-health researcher at Dartmouth, told me. Experts are far more worried about still-unanswered questions: How did it get into the milk? Marrazzo said. What does that say about the environment supporting that?
During this outbreak, experts have called for better testing and surveillancefirst of avian and mammalian wildlife, now of livestock. But federal agencies have been slow to respond. Testing of dairy cows was voluntary until last week. Now groups of lactating dairy cows must be screened for the virus before they move across state lines, but by testing just 30 animals, often out of hundreds. Michael Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told me he would also like to see more testing of other livestock, especially pigs, which have previously served as mixing vessels for flu viruses that eventually jumped into humans. More sampling would give researchers a stronger sense of where the virus has been and how its spreading within and between species. And it could help reveal the genomic changes that the virus may be accumulating. The U.S. Department of Agriculture and other federal agencies could also stand to shift from almost this paternalistic view of, Well tell you if you need to know, Osterholm said, to greater data transparency. (The USDA did not respond to a request for comment.)
Testing and other protections for people who work with cows have been lacking, too. Many farm workers in the U.S. are mobile, uninsured, and undocumented; some of their employers may also fear the practical and financial repercussions of testing workers. All of that means a virus could sicken farm workers without being detectedwhich is likely already the casethen spread to their networks. Regardless of whether this virus sparks a full-blown pandemic, we are completely ignoring the public-health threat that is happening right now, Jennifer Nuzzo, the director of the Pandemic Center at the Brown University School of Public Health, told me. The fumbles of COVIDs early days should have taught the government how valuable proactive testing, reporting, and data sharing are. Whats more, the pandemic could have taught us to prioritize high-risk groups, Sosin told me. Instead, the United States is repeating its mistakes. In response to a request for comment, a CDC spokesperson pointed me to the agencys published guidance on how farmworkers can shield themselves with masks and other personal protective equipment, and argued that the small number of people with relevant exposures who are displaying symptoms has been adequately monitored or tested.
Other experts worry that the federal government hasnt focused enough on what the U.S. will do if H5N1 does begin to rapidly spread among people. The countrys experience with major flu outbreaks is an advantage, especially over newer threats such as COVID, Luciana Borio, a former acting chief scientist at the FDA and former member of the National Security Council, told me. But she worries that leaders are using that notion to comfort ourselves in a way that I find to be very delusional. The national stockpile, for instance, includes only a limited supply of vaccines developed against H5 flu viruses. And they will probably require a two-dose regimen, and may not provide as much protection as some people hope, Borio said. Experience alone cannot solve those challenges. Nor do the nations leaders appear to be adequately preparing for the wave of skepticism that any new shots might meet. (The Department of Health and Human Services did not respond to a request for comment.)
In other ways, experts told me, the U.S. may have overlearned certain COVID lessons. Several researchers imagine that wastewater could again be a useful tool to track viral spread. But, Sosin pointed out, that sort of tracking wont work as well for a virus that may currently be concentrated in rural areas, where private septic systems are common. Flu viruses, unlike SARS-CoV-2, also tend to be more severe for young children than adults. Should H5N1 start spreading in earnest among humans, closing schools is probably one of the single most effective interventions that you could do, Bill Hanage said. Yet many politicians and members of the public are now dead set on never barring kids from classrooms to control an outbreak again.
These misalignments arent limited to H5N1. In recent years, as measles and polio vaccination rates have fallen among children, caseseven outbreaksof the two dangerous illnesses have been reappearing in the United States. The measles numbers are now concerning and persistent enough that Nahid Bhadelia worries that the U.S. could lose its elimination status for the disease within the next couple of years, undoing decades of progress. And yet public concern is low, Helen Chu, an immunologist and respiratory-virus expert at the University of Washington, told me. Perhaps even less thought is going toward threats abroadamong them, the continued surge of dengue in South America and a rash of cholera outbreaks in Africa and southern Asia. Were taking our eye off the ball, Anthony Fauci, NIAIDs former director, told me.
That lack of interest feels especially disconcerting to public-health experts as public fears ignite over H5N1. We dont put nearly enough emphasis on what is it that really kills us and hurts us, Osterholm told me. If anything, our experience with COVID may have taught people to further fixate on novelty. Even then, concern over newer threats, such as mpox, quickly ebbs if outbreaks become primarily restricted to other nations. Many people brush off measles outbreaks as a problem for the unvaccinated, or dismiss spikes in mpox as an issue mainly for men who have sex with men, Ajay Sethi, an infectious-disease epidemiologist at the University of Wisconsin at Madison, told me. And they shrug off just about any epidemic that happens abroad.
The intensity of living through the early years of COVID split Americans into two camps: one overly sensitized to infectious threats, and the other overly, perhaps even willfully, numbed. Many people fear that H5N1 will be the next big one, while others tend to roll their eyes, Hanage told me. Either way, public trust in health authorities has degraded. Now, no matter what happens, you could be accused of not sounding the alarm, or saying, Oh my God, here we go again, Jeanne Marrazzo told me. As long as infectious threats to humanity are growing, however, recalibrating our sense of infectious danger is imperative to keeping those perils in check. If a broken barometer fails to detect a storm and no one prepares for the impact, the damage might be greater, but the storm itself will still resolve as it otherwise would. But if the systems that warn us about infectious threats are on the fritz, our neglect may cause the problem to grow.
Public health officials are continuing to monitor as an outbreak of avian flu, also known as bird flu, continues to spread across the country.
The strain, known as H5N1, has sickened several mammals this year, according to the Centers for Disease Control and Prevention (CDC), the U.S. Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA).
Several dairy cows have been infected, resulting in milk samples showing inactive remnants of the virus, and one human case has been confirmed.
Health officials say the food supply is safe and the risk to the general public is currently low.
Here's the latest to know on the outbreak.
Avian influenza, or bird flu, is an infectious viral disease that primarily spreads among birds and is caused by infection with Influenza A viruses.
These viruses typically spread among wild aquatic birds but can infect domestic poultry and other bird and animal species, according to the CDC.
Although bird flu viruses normally don't infect humans, there have been rare cases of infection. To confirm infection, laboratory testing is required.
Signs and symptoms of infection in humans often include sore throat, cough, fever, runny or stuffy nose, headache, muscle or body aches, fatigue and shortness of breath. Less common symptoms include nausea, vomiting, diarrhea and seizures.
Infections can range from no symptoms or mild illness, such as flu-like symptoms, to more severe illness, such as pneumonia that could require hospitalizations, the CDC says.
In early March, the USDA announced a bird flu strain that had sickened millions of birds across the U.S was identified in several mammals this year.
At the time, three states had reported cases of bird flu in mammals in 2024, including striped skunks found in Washington state, a mountain lion in Montana and a raccoon in Kentucky.
A few weeks later, federal and state public health officials said they were investigating an illness among primarily older dairy cows in Kansas, New Mexico and Texas and causing symptoms including decreased lactation and low appetite.
The USDA said in a statement at the time that "there is no concern about the safety of the commercial milk supply or that this circumstance poses a risk to consumer health."
Earlier this month, the CDC said a human case of bird flu was identified in Texas and linked to cattle. The infected individual worked directly with sick cattle and reported eye redness as their only symptom.
This is the second human case of H5N1 ever reported in the U.S. but the first linked to cattle.
However, there have been no reports and no evidence to indicate there is person-to-person transmission, a CDC Director Dr. Mandy Cohen told ABC News at the time.
The CDC said it considers the health risk assessment to the general public to be low.
Earlier this week, reports emerged of bird flu fragments found in samples of pasteurized milk. However, the fragments are inactive remnants of the virus and cannot cause infection as the commercial milk supply undergoes pasteurization.
Federal agencies maintain the U.S. commercial milk supply remains safe because milk is pasteurized and dairy farmers are required to dispose of any milk from sick cows, so it does not enter the supply.
"To date, we have seen nothing that would change our assessment that the commercial milk supply is safe," the FDA said in an update.
The FDA said in its update that fragments of the virus are likely inactivated by the pasteurization process.
"The discovery of bird flu virus fragments in commercial milk is significant, not because it poses a direct threat to public health, but because it indicates a broader exposure among dairy cattle than we previously understood," said Dr. John Brownstein, an epidemiologist and chief innovation officer at Boston Children's Hospital and an ABC News contributor. "This calls for an expanded surveillance of both the virus's presence and its potential impact on food safety."
He added, "It's crucial to continue rigorous testing to determine if any live virus can survive the process. Understanding the dynamics of this virus in dairy products will help us refine our risk assessments and ensure public health safety."
The FDA said it is collaborating closely with the CDC's food safety group surveillance team to monitor emergency department data and flu testing data for any unusual trends in flu-like illness, flu or conjunctivitis. There is currently no data showing any unusual trends or activity.
ABC News Sony Salzman contributed to this report.
New federal rules aimed at limiting the spread of the H5N1 bird flu virus among dairy cattle go into effect Monday, but detailed guidance documents released Friday by the U.S. Department of Agriculture reveal its mandatory testing order is less stringent than initially described.
While that is easing concerns from farmers and veterinarians about the economic and logistical burden of testing, it leaves questions about how effective the testing program will be at containing additional outbreaks.
More testing is better, said Jennifer Nuzzo, an epidemiologist and director of Brown Universitys Pandemic Center. But in many ways this policy is very leaky in terms of how much virus it will allow to move. And because we still dont know whats driving transmission between cows, we should not pin our hopes on this policy making a major dent in the infections were seeing.
On Wednesday, the USDA issued a federal order requiring farms to ensure lactating dairy cows test negative before being moved across state lines. Laboratories and state veterinarians also must report to the USDA any animals that have tested positive for H5N1 or any other influenza A virus. The guidance issued Friday narrowed the scope of that order.
It says farmers only have to test up to 30 animals in a given group. The guidance does not say how farmers should determine which 30 animals to test in larger groups that are being readied to be moved. The USDA did not respond to STATs questions about the rationale for the 30-animal cap.
Jamie Jonker, chief scientific officer for the National Milk Producers Federation, said the group supports the testing program as an important step in response to the outbreak, one that dairy farmers are ready to take as part of their responsibility to ensure the safety of their animals and the milk supply.
While pragmatic, researchers who spoke to STAT were split on whether the policy will be effective. Anice Lowen, an influenza researcher at Emory University School of Medicine, told STAT via email that the approach is likely sufficient to detect an H5N1-positive herd. I think this approach is reasonable, she said.
Nuzzo had concerns, however, that in very large herds, like those around 500 or more, infected animals could be missed. In herds where outbreaks have occurred, only somewhere between 5% to 15% of cows have presented with clinical symptoms, Terry Lehenbauer, a bovine disease epidemiologist and director of the Veterinary Medicine Teaching and Research Center at UC Davis, told STAT. My general experience would suggest that there are not a lot of lactating cattle that get shipped interstate on a regular basis, so were probably looking at fairly small numbers of animals that will be required, he said.
The federal order is in recognition of epidemiological evidence that the virus is spreading between cows in affected herds and between herds as cattle are moved. As of April 26, H5N1 outbreaks have been confirmed in 34 dairy herds in nine states, with the first outbreak in Colorado reported Friday.
But analysis of viral genomes from cows infected with H5N1, combined with evidence that genetic traces of the virus have been found broadly in milk in grocery stores, indicate that the outbreak is much more widespread.
The risk of infection from ingesting milk is believed to be very low because pasteurization should kill the virus. Academic researchers did not find any live virus in a small study of commercial milk products. The U.S. Food and Drug Administration is conducting its own, much larger study on the viability of virus in milk, results from which are expected in the coming days. On Friday, the FDA issued an update saying that tests of several samples of retail powdered infant and toddler formula were negative, indicating no presence of H5N1 viral fragments or whole virus. It provided no details on the quantity tested.
Because farmers are required to divert milk from sick animals out of the national food supply, the traces of H5N1 in grocery store products indicates that asymptomatic animals may also be shedding the virus. In an FAQ posted online Thursday, the USDA confirmed that cows without signs of illness can still test positive for virus, acknowledging it had found H5N1 in the lungs of an asymptomatic cow in an affected herd.
Under the new rules, cows that are to be moved between states must have samples collected and tested no more than a week prior to transport. A licensed or accredited veterinarian has to collect the samples between 3 and 10 milliliters of milk per animal taken from each of the four teats. Thats very important, the USDA noted, because there have been reports of infected animals having virus in only one teat.
A strange feature of H5N1s jump from birds into cows is that the virus seems to have developed an affinity for mammary tissue. Samples from sick cows show the highest levels of virus not in their noses but in their milk, suggesting that udders seem to be where H5N1 migrates to or infects.
The USDA order does not apply to beef cattle or non-lactating dairy cattle, including calves, due to their lower risk profile, according to the guidance. But influenza researchers told STAT that not enough yet is known about the risks to non-lactating animals to leave them out. Testing such cattle destined to move between states would not only guard against interstate spread of the virus, it would give important insight into the susceptibility of non-lactating animals, Lowen said.
Thijs Kuiken, a professor of comparative pathology in the Department of Viroscience at Erasmus Medical Center in Rotterdam, is particularly concerned about the potential for milk from infected cows to harm calves. The U.S. Food and Drug Administration has encouraged farmers to discard milk from H5N1-positive cows, but if thats not possible and farmers intend to feed calves with that milk, they should first heat it to kill any viruses and bacteria.
Newborn calves need to consume colostrum, the antibody-rich milk cows produce in the first few days after birth, in order to start building their immune systems to ward off all the microbial threats that exist on a farm. Without it, calves often quickly succumb to infection.
If a farmer doesnt know that a cow has H5N1 because its not showing symptoms, calves could inadvertently be consuming the virus. The reason that has Kuiken worried is because of a cluster of fatal H5N1 cases in baby goats, reported in Minnesota in March. Genomic analyses showed they likely contracted the virus from a backyard poultry flock that had been depopulated due to H5N1 days before the goats were born. The animals had shared the same enclosure, including a water source that was likely contaminated. Ten of the kids died after showing neurological symptoms; necropsies on five of them showed virus in the brains and other organs.
Because we dont know the extent of this virus in dairy herds in North America, Kuiken said, I would expect there will be neurologically affected calves turning up sometime. My prediction is that if it has not already happened, that young dairy calves on affected farms will be found with severe highly pathogenic avian influenza H5N1 infection.
At this time, there have been no reported cases of H5N1-positive dairy cattle exhibiting any signs of neurological disease in the U.S.
Correction: An earlier version of this article misspelled Thijs Kuikens surname.
Helen Branswell contributed reporting.
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A senior official from the US Food and Drug Administration (FDA) said today that its nationwide survey of retail milk has found remnants of H5N1 avian flu viruses in one in five samples, with the highest concentrations in regions where outbreaks in dairy cattle have been reported.
Donald Prater, DVM, acting director of the FDA Center for Food Safety and Applied Nutrition (CFSAN), shared the new findings with state health officials who took part in a scientific symposium on H5N1 hosted by the Association of State and Territorial Health Officials (ASTHO). The results come in the wake of earlier findings this week from more limited FDA sampling, along with similar findings from a smaller set of samples tested by a lab that's part of the National Institute of Allergy and InfectiousDiseases Centers of Excellence for Influenza Research and Response (CEIRR) Network.
At today's ASTHO briefing, state health officials heard the latest investigation and research updates from federal health officials and had the opportunity to ask their own questions, everything from virus shedding in cow manure to pandemic preparedness.
Prater reiterated that the FDA hasn't changed its assessment that the nation's milk supply remains safe. So far, early work on milk samples that were positive for H5N1 fragments haven't found any viable (potentially infectious) virus.
He said, however, that the FDA still has a long list of data gaps to fill, including identifying the risk of infection to humans via oral consumption and validating that existing pasteurization methods can inactivate H5N1.
Other data gaps include how long the virus survives in raw milk and the infectious dose of viruses. Though a major concern is retail milk, Prater also said the FDA needs to see if contamination is occurring in other products, such as cheese made from raw milk.
Rosemary Sifford, DVM, deputy administrator for veterinary services and chief veterinarian with the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) said the agency has now shared 260 genetic sequences with public databases, up from 239 earlier this week. Of those, only 1 had a mutation linked to mammalian adaptation.
She also said the B3.13 genome circulating in cattle was first seen in poultry in the middle of March in a Texas flock at a time when the virus was cropping up in some of the state's dairy farms. Sifford said investigators continue to look at how the virus is moving on farms and how it transmits among cattle.
Scientists are looking for the virus in other species, including feral pigs, and regular influenza surveillance is monitoring the situation in commercial pigs. Sifford said efforts are under way to gauge how long infected cows shed the virus and if shedding patterns are any different in asymptomatic animals.
When asked about on-farm transmission, she said scientists haven't observed significant shedding in cow feces. Meanwhile, sampling from the USDA's Food Safety and Inspection Service (FSIS) found the highest concentrations in milk and mammary tissue.
Centers for Disease Control and Prevention (CDC) officials shared more details from their epidemiologic investigations, including virus findings in other animals on affected dairy farms. Sonja Olsen, PhD, associate director for preparedness and response with the CDC's Influenza Division, said there were 6 H5N1 positive tests in cats from three states: 3 in Texas, 2 in New Mexico, and 1 in Ohio.
Also, there were 5 H5N1 detections in wild birds on the farms.
She said CDC a key question is the infection risk from exposure to milk and whether certain conditions, such as aerosolization, pose a higher risk.
Vivien Duggan, PhD, who heads the CDC's Influenza Division, said the interagency Flu Risk Management group, which formed 15 years ago, is meeting now to discuss prepandemic vaccines and diagnostics.
On the research front, the CDC is looking for any changes in the virus that would hamper the ability to use countermeasures, such as antiviral drugs and vaccines.
A key tool that the CDC uses to evaluate and prioritize resources is the Influenza Risk Assessment Tool (IRAT), in which its experts grade the virus using 10 data criteria. Duggan said the CDC is still gathering some data and that it will take some time to evaluate the virus and come up with a risk score. In its last assessment in July 2023, the agency scored the H5N1 clade 2.3.4.4b virus from a Spanish mink farm outbreak as slightly higher for some elements than a 2022 virus from the same clade from wild birds.
So far, research results have been promising for antiviral susceptibility. And for the two candidate vaccine viruses against the H5N1 2.3.4.4b clade, experiments using ferret antisera show good cross-reaction against the outbreak strain, she said.
When state officials asked what would trigger ramped up H5N1 vaccine production, Duggan said officials are watching for certain cues, such as change in mammalian transmission, better adaptation to human-to-human spread, and clusters of cases. "There's no formula, but we're all on the watch."
Health officials also heard from government countermeasure experts, who said they don't foresee any issues with the antiviral supply chain.
State health officials had several questions about where things stand with a candidate vaccine. David Boucher, PhD, director of infectious disease preparedness and response at the Department of Health and Human Services Administration for Strategic Preparedness, said there is a limited quantity of prefilled syringes and vials that are used for clinical trials, for example. He added that health officials are already looking at regulatory pathways to use the vaccine more widely, if needed.
He said the first wave of production, if needed, could provide several hundreds of thousands of vaccine doses, and the second tranche could amount to 10 million doses. "Any pivot from that would require additional resources," Boucher said. "If we need to pull any of those levers, we're willing to do so."
Partnering with established seasonal flu vaccine producers has the benefit of a licensed platform in place that can be easily adapted to include an H5N1 vaccine virus, but he acknowledged that a downside would be a potential disruption in seasonal flu vaccine production. "There are a lot of variables that go into making that decision."
Two safety and immunogenicity studies are already under way on candidate H5N1 vaccines, Boucher told the group.
In mid-March, a mysterious disease began to spread among cows at a north Texas dairy farm. Just a few days later, cats on the farm started acting strange.
Their eyes and noses leaked copiously, they walked incessantly in circles, their bodies grew stiff, and they lost their sight and coordination. Then, they began to die.
According to officials at the US Centers for Disease Control and Prevention (CDC), a dozen of the domestic felines on this one farm were the casualties of a highly contagious strain of bird flu. They seem to have contracted the virus from drinking raw, unpasteurized milk from cows on the property.
The cats are merely the latest victims in a continued outbreak of bird flu, which first entered the US in late 2021, and has since jumped from birds to mammals, such as foxes, raccoons, possums, skunks, seals, leopards, bears, mountain lions, and bobcats.
On March 25, the US Department of Agriculture reported the first confirmed case of bird flu ever identified among cows.
Several dairy farms in Kansas and Texas were affected, and later, their cows carried the virus to Michigan, Idaho, and Ohio when they were transported interstate.
Despite one farm worker falling ill from the virus through contact with the cows, so far this outcome is extremely rare. Little more than a handful of cases of this bird flu strain have infected humans worldwide and only one of these cases is likely to have involved mammal to human transmission, not bird to human transmission.
Officials have assured the public that drinking pasteurized dairy milk will not expose them to the virus. The Food and Drug Agency is carrying out extensive milk product tests, and it has detected no signs of the virus as of yet.
Unfortunately, the dozen or so domestic cats that died on the dairy farm in north Texas contracted the virus before farmers knew what pathogen they were dealing with. Unknowingly, they fed their cats contaminated milk.
Cows in the US that are sick with bird flu are producing thick and syrupy milk, but perhaps this symptom isn't as apparent in the early days of illness.
The first cat to show signs of sickness on the north Texas dairy farm was recorded a mere day after the first cow fell ill.
On March 21, samples of cow milk from the affected dairy farms and two deceased cats from these farms were donated to a diagnostic lab at the Iowa State University (ISU). The cats tested positive for the influenza A virus (IAV).
Cases of bird flu among cats are globally well-documented. Our feline pets are especially susceptible to the virus when in contact with sick birds, but the transfer from cows has never been previously reported.
Researchers at ISU say the cow and cat samples they analyzed contained signs of IAV with "a notable degree of similarity", which suggests a "shared origin" for the strain.
"Although exposure to and consumption of dead wild birds cannot be completely ruled out for the cats described in this report, the known consumption of unpasteurized milk and colostrum from infected cows and the high amount of virus nucleic acid within the milk make milk and colostrum consumption a likely route of exposure," write the team of researchers, led by pathologist Eric Burrough.
The findings suggest bird flu can jump from mammal to mammal, which may make the contagion harder to control. Even among cows, experts still aren't sure how the virus is transmitted.
As the public waits for more answers, one thing is clear: pasteurized milk is the safest option of all. For both humans and cats.
