Dairy cows have not been affected before in the United States, or anywhere else in the world to my knowledge, and we've never before seen such clear evidence of mammal-to-mammal transmission.
“A colleague of mine, he told me, ‘You know what’s strange? I went to one of my dairies last week, and all their cats were missing. I couldn’t figure it out — the cats usually come to my vet truck,’ ” Petersen recalled. “And then someone called me and said half of his cats had passed away without warning, and so then all the alarm bells start going off in your head.”
The cats had died from swollen brains, a potential result of influenza.
The H5N1 bird flu outbreak in dairy cows in the United States has likely been going on for months longer than was previously realized, and has probably spread more widely across the country than the confirmed outbreaks would imply, according to an analysis of genetic sequences that were released Sunday by the U.S. Department of Agriculture. (...)
The genetic sequences cluster too closely for this to be anything other than a single spillover, Worobey said. “If it were jumping from bird to cattle over and over again … I wouldn’t think you would just get this same very reduced genetic diversity where each of the internal segments are showing the same pattern.”
State Veterinarian Dr. Nora Wineland says the spread of the virus on dairies has been inconsistent.
“There are farms that have been closed farms, not adding new cattle in, and yet they’re still able to get it,” she explains.
Cattle Farming
Before March 2024 there were no reports about H5N1 infections in cows outside of a laboratory experiment with high viral doses. Cattle was considered to not be very susceptible to influenza in general. Keeping large quantities of cows, often outside on pastures, has so far been considered a minor risk from a public health perspective. However, large quantities of infected cows now enable long chains of infection and spillback into wild birds, resulting in additional human and poultry infections. The infections of cows with H5N1 coincide with the first documented cases of H5N1 in goats. Once again the issue is exacerbated by a lack of surveillance.
As this disease spreads, dairy farmers like me are increasingly worried about the health of our animals, the safety of our farm workers, and the outlook for our markets, especially since the industry has already suffered from extreme price volatility in recent years that has pushed thousands of farm families out of business.
Our findings show that HPAIV (H5N1) has the potential to infect bovine calves, at least after high-titer intranasal inoculation, and that conventional HI tests may underestimate such infections. Furthermore, asymptomatic shedding of HPAIV (H5N1) by infected calves and subsequent seroconversion seem to be possible, and even low levels of HPAIV (H5N1) might be sufficient to induce a detectable antibody response in contact calves. However, the possibility that the infectivity detected in the contact calf at 1 dpi was the result of residual inoculum cannot be ruled out. Although the question whether calf-to-calf transmission of HPAIV (H5N1) occurs could not be definitely answered by our study, bird-to-calf transmission resulting in seroconversion is probable.
As of Monday, March 25, unpasteurized, clinical samples of milk from sick cattle collected from two dairy farms in Kansas and one in Texas, as well as an oropharyngeal swab from another dairy in Texas, have tested positive for highly pathogenic avian influenza (HPAI). Additional testing was initiated on Friday, March 22, and over the weekend because farms have also reported finding deceased wild birds on their properties. Based on findings from Texas, the detections appear to have been introduced by wild birds. Initial testing by the National Veterinary Services Laboratories has not found changes to the virus that would make it more transmissible to humans, which would indicate that the current risk to the public remains low.
Our findings are that there are closer to 1.5 billion cows worldwide. However, according to 2023 studies by USDA, there are approximately 1 billion (942,630 to be exact) cattle stocks in the world.
In 2014, according to Our World in Data, cattle stocks numbered 1.47 billion head of cattle worldwide.
It's perhaps not as well known as it should be that many 'strict herbivores' will eat animal matter on occasion. Sometimes this behaviour is absolutely deliberate and likely motivated by a need for calcium: antler- and bone-eating is common in deer and other hoofed mammals, and the consumption of seabird chick heads, wings and legs by island-dwelling deer and sheep is well documented (Furness 1988). Red deer Cervus elaphus that eat seabirds seem to deliberately eat the bones only, and carefully avoid ingesting the flesh. White-tailed deer Odocoileus virginianus and domestic cattle Bos taurus have been shown (thanks again to remote cameras) to consume passerine and quail nestlings and/or eggs when they discover them (Pietz & Granfors 2000, Nack & Ribic 2005, Ellis-Felege et al. 2008): this behaviour is likely opportunistic, but may well be common and widespread (it's difficult to document since it mostly occurs at night and no evidence remains).
For the dairies whose herds are exhibiting symptoms, on average about ten percent of each affected herd appears to be impacted, with little to no associated mortality reported among the animals.
"You get sick cows from one disease, then that creates a domino effect for other things, like routine pneumonia and digestive issues," Daly said.
A farm in Michigan killed about 10% of its 200 infected cows after they too failed to recover from the virus, said Phil Durst, an educator with Michigan State University Extension who spoke with that farm.
Michigan has more confirmed infections in cattle than any state as well as two of three confirmed cases of U.S. dairy workers who contracted bird flu.
In Colorado, some dairies reported culling cows with avian flu because they did not return to milk production, said Olga Robak, spokesperson for the state Department of Agriculture.
Ohio Department of Agriculture spokesperson Meghan Harshbarger said infected cows have died in Ohio and other affected states, mostly due to secondary infections.
The Texas Animal Health Commission also confirmed that cows have died from secondary infections at some dairy operations with avian flu outbreaks.
Officials could not provide figures for the number of statewide cow mortalities.
"You get sick cows from one disease, then that creates a domino effect for other things, like routine pneumonia and digestive issues," Daly said.
A farm in Michigan killed about 10% of its 200 infected cows after they too failed to recover from the virus, said Phil Durst, an educator with Michigan State University Extension who spoke with that farm.
Michigan has more confirmed infections in cattle than any state as well as two of three confirmed cases of U.S. dairy workers who contracted bird flu.
In Colorado, some dairies reported culling cows with avian flu because they did not return to milk production, said Olga Robak, spokesperson for the state Department of Agriculture.
Ohio Department of Agriculture spokesperson Meghan Harshbarger said infected cows have died in Ohio and other affected states, mostly due to secondary infections.
The Texas Animal Health Commission also confirmed that cows have died from secondary infections at some dairy operations with avian flu outbreaks.
Officials could not provide figures for the number of statewide cow mortalities.
>20% of farms received cattle within 30 days of clinical
signs; and
>60% of farms continued to move animals off the farm
after onset of clinical signs.
>50% of farms used trucks and trailers that are shared
with other farms to transport livestock within 30 days
prior to onset of clinical signs; and
>50% of farms that used shared vehicles do not clean
vehicles prior to use.
>20% of dairies’ employees visit other dairies within 30
days of onset of clinical signs;
>20% of dairies’ employees own livestock or poultry at
their personal residence;
>30% of dairies’ employees work at another farm with
livestock; most of these employees work on another
dairy; and
20% of dairies’ employees have family members who
work at another farm with livestock
Mammal-to-Mammal Transmission
Mammal-to-mammal transmission has been observed between cows and from cows to other species, namely cats, a racoon, and humans. Milk and milking instruments seem to be the primary cause of the transmission, due to high concentrations of virus found in milk. Apparently the outbreak started as early as late December 2023 and was not detected for months. The virus has spread to at least 170 farms in at least 13 US states. Testing of milk reveals that the presence of bird flu in cows is a widespread phenomenon.
This is one of the first times that we are seeing evidence of efficient and sustained mammalian-to-mammalian transmission of highly pathogenic avian influenza H5N1
Whole viral genome sequences recovered from dairy cows, birds, domestic cats, and a raccoon from affected farms indicated multidirectional interspecies transmissions. Epidemiologic and genomic data revealed efficient cow-to-cow transmission after apparently healthy cows from an affected farm were transported to a premise in a different state. These results demonstrate the transmission of HPAI H5N1 clade 2.3.4.4b virus at a non-traditional interface underscoring the ability of the virus to cross species barriers.
So far, 11 human cases have been reported in the U.S., with the first dating back to April 2022, each with mild symptoms: four were linked to cattle farms and seven have been linked to poultry farms, including an outbreak of four cases reported in the last few weeks in Colorado. These recent patients fell ill with the same strain identified in the study as circulating in dairy cows, leading the researchers to suspect that the virus likely originated from dairy farms in the same county. (...) Sequencing also showed that the virus was transmitted to cats, a raccoon and wild birds that were found dead on affected farms. The cats and raccoon most likely became ill from drinking raw milk from infected cows. Though it isn’t known how the wild birds became infected, the researchers suspect it may have resulted from environmental contamination or aerosols kicked up during milking or cleaning of the milking parlors.
To date, we have not found significant
concentration of virus in respiratory related samples,
which indicates to us that respiratory transmission is
not a primary means of transmission.
It is quite intriguing that bovines were largely unaffected by influenza A, even though most of the domesticated and wild animals/birds at the human–animal interface succumbed to infection over the past few decades. Influenza A occurs on a very infrequent basis in bovine species and hence bovines were not considered to be susceptible hosts for influenza until the emergence of influenza D.
Yet decades earlier, researchers from Canada's department of agriculture were conducting "preliminary" experiments on lactating dairy cows to see what would happen when the animals were infected with several types of viruses.
Their 1953 paper showed that a type of human influenza A could infect cows' mammary glands, leading to live virus in milk secretions.
Kelvin's own research, published in 2015, probed the issue further.
Her team explored influenza transmission between mother and infant ferrets, an animal scientists typically rely on for flu research since ferrets' airway receptors are the most similar to humans'.
If there is cow-to-cow transmission, how does it work? It’s clear that it’s dairy cows, and it could be that it’s due to the milking instruments that do not get cleaned enough. It’s human driven cow-to-cow transmission. And if that’s the case, you can stop it.
As of Monday, March 25, unpasteurized, clinical samples of milk from sick cattle collected from two dairy farms in Kansas and one in Texas, as well as an oropharyngeal swab from another dairy in Texas, have tested positive for highly pathogenic avian influenza (HPAI). Additional testing was initiated on Friday, March 22, and over the weekend because farms have also reported finding deceased wild birds on their properties. Based on findings from Texas, the detections appear to have been introduced by wild birds. Initial testing by the National Veterinary Services Laboratories has not found changes to the virus that would make it more transmissible to humans, which would indicate that the current risk to the public remains low.
The Texas Department of State Health Services is reporting a human case of avian influenza A(H5N1) virus in Texas. The case was identified in a person who had direct exposure to dairy cattle presumed to be infected with avian influenza.
Allogrooming, which generally involves one cow licking another around the head and neck, is believed to serve a number of social purposes. For instance, social grooming is both a way to establish individual bonds between members of a group and also enhances overall social cohesion in the herd.
Has USDA confirmed at this point that cow-to-cow
transmission is a factor?
Yes, although it is unclear exactly how virus is being
moved around. We know that the virus is shed in milk at
high concentrations; therefore, anything that comes in
contact with unpasteurized milk, spilled milk, etc. may
spread the virus.
The report of the US human case brings forth several important issues including the question of whether this signals a global pandemic in the making? Foremost, how has transmission in cows and from cow to human occurred? Infected cows show symptoms such as decreased lactation, anorexia, lethargy, fever and dehydration, raising concerns of an increased risk of H5N1 viruses becoming better adapted to mammals with enhanced potential to spilling over to humans and other livestock. It has been suggested that A(H5N1) might not be spreading among cows through the air. The current thought is that the virus has spread via the use of contaminated milking equipment between infected and uninfected cows. How a virus that causes respiratory tract disease ends up in cow udders, and is detectable in milk, and whether other organs are infected is important to elucidate. No infection in beef cattle has been detected yet, but this could be due to sub-clinical or mild symptoms and lack of active surveillance.
Scaling up of the production of human vaccines against the new A(H5N1) variants seems imperative, primarily to protect high-risk individuals such as farm workers against infection, but also for stockpiling, and secondly to increase preparedness should the virus evolve to sustained human-to-human transmission. Culling of poultry has so far not resulted in controlling the zoonotic pandemic (enzootic) of A(H5N1); perhaps a shift towards prevention instead, by the vaccination of farm animals and farm workers needs to be considered.
It is quite intriguing that bovines were largely unaffected by influenza A, even though most of the domesticated and wild animals/birds at the human–animal interface succumbed to infection over the past few decades. Influenza A occurs on a very infrequent basis in bovine species and hence bovines were not considered to be susceptible hosts for influenza until the emergence of influenza D.
A strain of highly pathogenic avian influenza has been silently spreading in US cattle for months, according to preliminary analysis of genomic data. The outbreak is likely to have begun when the virus jumped from an infected bird into a cow, probably around late December or early January. This implies a protracted, undetected spread of the virus — suggesting that more cattle across the United States, and even in neighbouring regions, could have been infected with avian influenza than currently reported. (...)
Analysis of the genomes suggests that the cattle outbreak probably began with a single introduction from wild birds in December or early January. (...) The data also show occasional jumps back from infected cows to birds and cats. “This is a multi-host outbreak,” says Nelson.
The genomic data reveal that the viral genome sequenced from the infected person does not include some of the signature mutations observed in the cattle. “That is a mystery to everyone,” says Nelson.
One possibility is that the person was infected by a separate viral lineage, which infected cattle that have not been swabbed. Another less likely scenario, which can’t be ruled out, says Nelson, is that the person was infected directly from a wild bird. “It raises just a whole slew of questions about what black box of samples we are missing.”
We genetically characterize HPAI viruses from dairy cattle showing an abrupt drop in milk production. They share nearly identical genome sequences, forming a new genotype B3.13 within the 2.3.4.4b clade. B3.13 viruses underwent two reassortment events since 2023 and exhibit critical mutations in HA, M1, and NS genes but lack critical mutations in PB2 and PB1 genes, which enhance virulence or adaptation to mammals.
On 3 May, Richard Webby at St. Jude Children’s Research Hospital in Tennessee and his colleagues published preliminary results suggesting that the bird-like sialic acid is abundant in the udders of cows, explaining why H5N1 is able to infect udders.
Alarmingly, these findings suggested that the human-like variant is also common in the udder. This would mean that any H5N1 viruses with mutations that allow them to bind the human-like variant could survive and thrive in udders, and potentially spread to people.
However, de Vries’s team has now done a more detailed study that suggests the human-like receptor is not present in udders after all. (...) “The Dutch team did use a more sophisticated methodology,” says Webby. “I much prefer their conclusion.”
I want to emphasize really how unusual this is. In other mammalian species with influenza viruses, it's primarily a respiratory disease, which doesn't seem to be the case in these cattle.
Without changes in HA affecting receptor binding, the risk of the virus becoming transmissible between humans is low. The lack of HA changes may also suggest (at least with the current tissue tropism) that there is not strong selective pressure to change receptor binding, suggesting ‘avian-like’ α-2,3-linked sialic acids are abundant in the main sites of replication in these animals. However, this is also true for dogs and pigs, which in the short term do not strongly select for such changes, yet in the longer term, avian-origin H1N1 and H3N2 viruses in these species gradually adapt to ‘human-like’ α-2,6-linked sialic acids.
H5N1 is transmitting from cattle back into wild birds, poultry, cats, and other species.
These results indicate that deposited virus on milking equipment could remain infectious for long periods of time, posing a potential risk to humans as well as contributing to cow-to-cow transmission. Typically there is only 10-15 min between milking sessions with shared milking equipment, thus virus from an asymptomatic infected cow could remain on the material for multiple rounds milking sessions. These results are currently being validated with bovine H5N1 virus and preliminary data suggests a similar trend in stability, with < 2 log decay at 1 hour of incubation at 70% RH on both surfaces.
People who work on dairy farms, though, have reason to worry, Lakdawala added. In the so-called parlors where dairy cows are milked, animals are strapped into machines that latch on to their udders, pump until the rate of flow slows, then release, swinging “off the animal at eye height,” Lakdawala told me, and blasting bystanders with frothy liquid. The machines aren’t necessarily sanitized between each animal—and what cleaning does occur often involves a high-pressure hose-down that also mists up milk. The entire process involves a lot of direct maneuvering of udders, as workers load machinery onto each cow and prime their initial milk flow manually. If workers aren’t directly getting milk on their hands—which will, at some point, touch their face—they’re “constantly being bombarded with aerosols, droplets, and spray,” Lakdawala said.
The A(H5N1) virus from the human case in Texas spread efficiently between ferrets in direct contact but did not spread efficiently between ferrets via respiratory droplets. This is different from what is seen with seasonal flu, which infects 100% of ferrets via respiratory droplets. (...) The study, completed on Friday, May 31, found that A/Texas/37/2024 virus caused severe disease (100% lethal) in all six ferrets that were infected. This is consistent with what has been found recently in ferret studies with A(H5N1) viruses, including two published studies conducted in the past year. Ferrets infected with A(H5N1) viruses from mink in Spain (A/mink/Spain/3691-8_22VIR10586-10/2022) and from a person in Chile (A/Chile/25945/2023) had severe illness that was either fatal or required euthanasia. (...) In terms of spread, the CDC ferret study found that the A/Texas/37/2024 virus spread easily among ferrets (3 of 3 ferrets, or 100%) in direct contact with infected ferrets (placed in the same enclosure). However, the virus was less capable of spreading by respiratory droplets, which was tested by placing infected ferrets in enclosures next to healthy ferrets (with shared air but without direct contact). In that situation, only 1 of 3 ferrets (33%) became infected, and there was a one- or two-day delay in transmission with the A/Texas/37/2024 virus compared to transmission with seasonal flu viruses. This suggests that A/Texas/37/2024-like viruses would need to undergo changes to spread efficiently by droplets through the air, such as from coughs and sneezes.
The intensive, integrated, and specialized nature of the dairy industry results in biosecurity risks that are not
completely avoidable, but these risks can be mitigated. Given that disease spread between dairy and poultry
premises is multifactorial, mitigation measures that are integrated and target multiple risk factors are needed.
The USDA Federal Order requires premovement testing for interstate movement of lactating dairy cattle (as of
April 29, 2024) which greatly reduces the risk of premises-to-premises disease spread. Since 9 of 15 of the
affected dairy herds in Michigan were closed herds which did not bring any new cattle into the herd, restriction of
live cattle movements would not have prevented disease in these herds. Movement restrictions on cattle in
some Michigan affected herds may result in serious animal welfare issues since these specialized operations do
not have the facilities to manage all classes of dairy cattle and rely on an integrated network of operations to
raise and manage the different classes of cattle. However, testing before moving cattle would help limit
premises-to-premises transmission from cattle movement within the state and may identify additionally affected
herds.
As a first interim result, not only the US isolate but also a recent H5N1 virus from a wild bird in Germany was able to multiply very well in the udder. Following direct infection of the udder through the teats, the dairy cows in both cases showed clear signs of disease such as a sharp drop in milk production, changes in milk consistency and fever. (...) Direct infection of the udder by the virus seems to be of particular importance. Since the first detection of the pathogen 27 years ago in many countries, particularly in Asia, there has been possible contact of ruminants such as water buffalo and cattle with the faeces of infected wild birds, but no similar infection events have ever been observed. The exact circumstances that led to the outbreak in the USA are still unknown.
Here we characterize an HPAI H5N1 virus isolated from infected cow milk in mice and ferrets. Like other HPAI H5N1 viruses, the bovine H5N1 virus spread systemically, including to the mammary glands of both species, however, this tropism was also observed for an older HPAI H5N1 virus isolate. Bovine HPAI H5N1 virus bound to sialic acids expressed in human upper airways and inefficiently transmitted to exposed ferrets (one of four exposed ferrets seroconverted without virus detection). Bovine HPAI H5N1 virus thus possesses features that may facilitate infection and transmission in mammals.
By contrast, the Cow-H5N1 virus bound to both α2,3- and α2,6-linked sialic acids, indicating that the Cow-H5N1 virus may have the ability to bind to cells in the upper respiratory tract of humans. The dual receptor-binding specificity of Cow-H5N1 was confirmed by two independent replicate experiments (Extended Data Figs. 7 and 8).
However, Eisfeld and colleagues report dual binding specificity for α-2,3 and α-2,6-linked sialic acid receptors, which they hypothesize to be a specific feature of A/H5N1 viruses isolated from cattle. This finding suggests that one of the traits required for mammal-to-mammal transmission via the air is already present in Cow-H5N1. However, the α-2,6-linked sialic acid-binding specificity must be further investigated in detail, as others have reported different observations.
Milk
Milk is usually pasteurized and therefore safe to consume, since all pathogens including avian influenza are deactivated by the heat. Meanwhile opponents of public health measures once again emerge as public health threats and raw milk sales have increased.
When H5N1 avian influenza started spreading among dairy cattle across the U.S. this year, regulators warned against consuming unpasteurized milk. What happened? Raw milk sales went up.
Distributors of this unsafe-for-human-consumption product deny H5N1—which has the potential to sicken millions of people—is a danger. Dairy farmers decline to allow disease detectives onto their properties.
After 25 years of watching, waiting and worrying about bird flu, what finally tips it over into a pandemic could be American contrariness.
The human respiratory tract is a major site of avian influenza A(H5N1) infection. However, many humans infected with H5N1 present with gastrointestinal tract symptoms, suggesting that this may also be a target for the virus. In this study, we demonstrated that the human gut expresses abundant avian H5N1 receptors, is readily infected ex vivo by the H5N1 virus, and produces infectious viral particles in organ culture. An autopsy colonic sample from an H5N1-infected patient showed evidence of viral antigen expression in the gut epithelium. Our results provide the first evidence, to our knowledge, that H5N1 can directly target human gut tissues.
Distributors of this unsafe-for-human-consumption product deny H5N1—which has the potential to sicken millions of people—is a danger. Dairy farmers decline to allow disease detectives onto their properties.
After 25 years of watching, waiting and worrying about bird flu, what finally tips it over into a pandemic could be American contrariness.
As of Monday, March 25, unpasteurized, clinical samples of milk from sick cattle collected from two dairy farms in Kansas and one in Texas, as well as an oropharyngeal swab from another dairy in Texas, have tested positive for highly pathogenic avian influenza (HPAI).
At this stage, there is no concern about the safety of the commercial milk supply or that this circumstance poses a risk to consumer health. 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 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.
H5N1 virus lost infectivity after 30 min at 56°C
Pasteurization of milk, widely practiced in several countries, notably the United States, requires temperatures of about 63 °C (145 °F) maintained for 30 minutes or, alternatively, heating to a higher temperature, 72 °C (162 °F), and holding for 15 seconds (and yet higher temperatures for shorter periods of time).
The FDA recognizes two pasteurization methods: high-temperature short-time (HTST) and ultra-high-temperature (UHT) pasteurization. HTST pasteurization requires heating milk to 161°F for 15 seconds, while UHT pasteurization involves heating milk to 280°F for 2 seconds. The specific pasteurization requirements are stated in the Code of Federal Regulations, Title 21, Part 131, Subpart D, Section 131.150.
Consumers of unpasteurized milk and cheese are a small proportion of the U.S. population — 3.2 percent and 1.6 percent, respectively — but compared with consumers of pasteurized dairy products, they are 838.8 times more likely to experience an illness and 45.1 times more likely to be hospitalized.
Testing conducted by the Food and Drug Administration on pasteurized commercially purchased milk has found genetic evidence of the H5N1 bird flu virus, the agency confirmed Tuesday. But the testing, done by polymerase chain reaction, or PCR, cannot distinguish between live virus or fragments of viruses that could have been killed by the pasteurization process. (...) “Pasteurization kills much sturdier viruses than influenza, so we expect it to work,” said Andrew Pekosz, a molecular microbiologist who studies respiratory viruses at Johns Hopkins Bloomberg School of Public Health. “But it’d be great to have the data.
In conclusion, this article documents a pattern between an earlier time in which anxiety over falling wages and increasing domestic immigration focused on issues of meat and dairy consumption and current anxiety over stagnant wages, fears over immigration, and a reassertion of the consumption of milk and dairy as a proxy reassertion of white privilege.
One slide Dr. Novembre has folded into his recent talks depicts a group of white nationalists chugging milk at a 2017 gathering to draw attention to a genetic trait known to be more common in white people than others — the ability to digest lactose as adults. It also shows a social media post from an account called “Enter The Milk Zone” with a map lifted from a scientific journal article on the trait’s evolutionary history.
In most of the world, the article explains, the gene that allows for the digestion of lactose switches off after childhood. But with the arrival of the first cattle herders in Europe some 5,000 years ago, a chance mutation that left it turned on provided enough of a nutritional leg up that nearly all of those who survived eventually carried it. In the post, the link is accompanied by a snippet of hate speech urging individuals of African ancestry to leave America. “If you can’t drink milk,” it says in part, “you have to go back.”
In an inconvenient truth for white supremacists, a similar bit of evolution turns out to have occurred among cattle breeders in East Africa.
He knew the Food and Drug Administration was working on its own national survey of the milk supply. But he was impatient. So he and a graduate student went on a road trip: They collected 150 commercial milk products from around the Midwest, representing dairy processing plants in 10 different states, including some where herds have tested positive for H5N1. Genetic testing found viral RNA in 58 samples, he told STAT.
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.
In all matrices, including human milk, pasteurization at 62.5 °C was generally sufficient to reduce surviving viral load by several logs or to below the limit of detection. Holder pasteurization (62.5 °C, 30 min) of human milk should be sufficient to inactivate nonheat resistant viruses, including coronaviruses, if present.
These results indicate that deposited virus on milking equipment could remain infectious for long periods of time, posing a potential risk to humans as well as contributing to cow-to-cow transmission. Typically there is only 10-15 min between milking sessions with shared milking equipment, thus virus from an asymptomatic infected cow could remain on the material for multiple rounds milking sessions. These results are currently being validated with bovine H5N1 virus and preliminary data suggests a similar trend in stability, with <2 log="log" decay="decay" at="at" 1="1" hour="hour" of="of" incubation="incubation" 70%="70%" RH="RH" on="on" both="both" surfaces="surfaces">
Results show that 4.4% of U.S. adults reported consuming raw milk at least once in the past year, with 1.6% reporting frequent consumption of raw milk (once per month or more often) and 1.0% reporting consumption once per week or more often. The individuals who consumed raw milk in the previous 12 months were more likely to be younger, living in a rural area, and living in a state in which retail sale of raw milk is legal.
The animals showed signs of illness starting on day 1, including ruffled fur and lethargy. All the animals survived until day 4, when they were euthanized to determine virus titers in multiple organs. (...) Detection of virus in the mammary glands of two mice was consistent with the high virus load in the milk of lactating cows, even though these mice were not lactating. Collectively, our data indicate that HPAI A(H5N1) virus in untreated milk can infect susceptible animals that consume it.
Here, we provide results of two independent clade 2.3.4.4b experimental infection studies evaluating (i) oronasal susceptibility and transmission in calves to a US H5N1 bovine isolate genotype B3.13 (H5N1 B3.13) and (ii) susceptibility of lactating cows following direct mammary gland inoculation of either H5N1 B3.13 or a current EU H5N1 wild bird isolate genotype euDG (H5N1 euDG). Inoculation of the calves resulted in moderate nasal replication and shedding with no severe clinical signs or transmission to sentinel calves. In dairy cows, infection resulted in no nasal shedding, but severe acute mammary gland infection with necrotizing mastitis and high fever was observed for both H5N1 genotypes/strains. Milk production was rapidly and drastically reduced and the physical condition of the cows was severely compromised. Virus titers in milk rapidly peaked at 10^8 TCID50/mL, but systemic infection did not ensue. Notably, adaptive mutation PB2 E627K emerged after intramammary replication of H5N1 euDG. Our data suggest that in addition to H5N1 B3.13, other HPAIV H5N1 strains have the potential to replicate in the udder of cows and that milk and milking procedures, rather than respiratory spread, are likely the primary routes of H5N1 transmission between cattle.
In conclusion, calves inoculated oronasally presented signs of mild respiratory illness including nasal mucus secretions and coughing although these cannot be fully associated with outcomes of H5N1 inoculation, whereas intramammary infection of dairy cattle with both clade 2.3.4.4b isolates resulted in severe clinical disease in both cow groups requiring early euthanasia in some cases. Severe disease in lactating cows was accompanied by a drastic reduction in milk production and obvious changes in milk quality.
The fact that you can go into a supermarket and 30% to 40% of those samples test positive, that suggests there’s more of the virus around than is currently being recognized.
Poultry Litter
Poultry litter consists mostly of poultry excrement and is used as feed for livestock. It is fed to beef cows, but usually not dairy cows.
UC Davis’ Payne said that in California, poultry waste is processed at high virus-killing temperatures, so it is unlikely to be a concern. The practice is banned in the United Kingdom, European Union and Canada, where fears of spreading bovine spongiform encephalitis — mad cow disease — made such practices seem too risky.
Representatives of the beef and poultry industry argue that the overall costs to the beef industry – and, ultimately, the consumer – would far outweigh any ‘”limited” potential safety gains from banning poultry litter as a cattle feed. They also claim that any ban would exacerbate the existing problem of the mass disposal of poultry litter from factory farms. In defending their right to feed poultry litter to cattle, the National Cattlemen’s Beef Association recently said that “we must continue to look to the science to avoid over-regulating the industry and creating policy that doesn’t meet our objective of a safer animal health system.”
The fact that certain elements within the food and farming industry are willing to publicly defend the feeding of poultry litter to cattle – that is chicken feces, feathers and other poultry debris collected from the floors of factory farms – on the basis that this represents a “safer animal health system” is an appalling indictment of the state of US food and farming. It also is a stark warning to us all of the huge chasm that has emerged between how most of us think our food is being produced and the appalling practices that are justified by those who are so deeply embroiled in the drive to produce ever cheaper meat that they no longer have any sense of what is accepted as the norm.
Adding broiler litter to beef cattle rations at a level of 20% or higher (as fed basis) generally meets the animal's needs for crude protein, calcium, and phosphorus. (...) Broiler litter to be used for cattle feed should contain at least 75% dry matter. If litter contains less than 70% dry matter, wet spots and mold can be problems. Since litter may contain scrap metal, the material should be run through a hammermill equipped with a magnet to remove objects that may cause hardware disease. In addition, the material should be screened to remove pieces of wood, glass, etc.
Animal wastes represent a vast reservoir of cheap nutrients, particularly for ruminants. In most countries, waste, particularly from poultry, is easily collected, as it is concentrated in small areas, and its cost, as a raw material for feed, is generally the cost of transport alone. The only expensive item may be processing, but this cost is relatively small and is recoverable from the profit arising out of the low original cost. Feed costs for dairy or beef cattle usually represent 50–80% of the total production costs; this can be reduced to 20–40% by utilizing these new feed resources as donors of protein, minerals and other nutrients.(...)The calculated mean energy values of animal wastes for ruminants, estimated in Table 8, indicate that only broiler manure and broiler litter exhibit a TDN value comparable to conventional feed ingredients (Müller, 1975e). The other livestock wastes are low in feed energy, at levels comparable to crop residues.
It seems ghoulish, but it is a perfectly legal and common practice for chicken litter — the material that accumulates on the floor of chicken growing facilities — to be fed to cattle.
"Bovine Influenza A Virus (BIAV)"
"Bovine Influenza A Virus (BIAV)" is a marketing term designed to distract from the fact that cows get bird flu.
But the American Association of Bovine Practitioners (AABP), an organization of beef and dairy veterinarians, declared in a statement (condemned by public health experts) last week that it doesn’t believe bird flu in cows should be considered bird flu at all.
“The AABP will call this disease Bovine Influenza A Virus (BIAV),” the association’s executive director K. Fred Gingrich II and president Michael Capel said in a statement, encouraging federal and state regulators to do the same. “It is important for the public to understand the difference to maintain confidence in the safety and accessibility of beef and dairy products for consumers.”
In other words, industry vets are trying to rebrand bird flu so that we keep calm and keep buying cheeseburgers. “They’re worried about selling products,” bovine veterinarian James Reynolds, a professor at Western University’s vet school, told me, calling the group’s statement “disease-washing.”
What is the appropriate nomenclature for this virus, now that it has appeared in dairy cows?
From USDA’s perspective, highly pathogenic avian influenza or H5N1 are the most scientifically accurate terms to describe this virus. This is also consistent with what the scientific community has continued to call the virus after it has affected other mammals.
Biosecurity
So far there is no readily available vaccine, no culling of infected herds, but at least limited mandatory testing of cattle herds being moved across USA state borders, testing of wastewater, and in Colorado testing of bulk milk tanks. While an important factor is that bird flu in cows is a new phenomenon, and testing resources are always limited, there is also no economic incentive to cull or even vaccinate cattle. While infected dairy cows produce less milk, this doesn't apply to beef cattle.
We don’t have a good sense of the spread because testing is voluntary and certainly not being done in a systematic way. We’re pretty much flying blind with the testing aspect.
ARS has begun to assess the potential to develop an
effective vaccine for H5N1 in bovine. It is difficult to
predict how long development might take, as many
outstanding questions remain about the transmission to
cattle, characterizations of the infection, etc.
It is important to keep in mind that while H5N1 is highly
pathogenic in birds, that is not the case in cattle. At this
time, APHIS does not think it would be practical,
feasible or necessarily informative to require mandatory
testing, for several reasons ranging from laboratory
capacity to testing turnaround times. We are working
actively to learn more about the emergence of H5N1 in
cattle, but right now we are seeing that a small portion
of the affected herds are becoming ill, and that the
number of herds exhibiting symptoms is relatively small.
For context, there are more than 26,000 dairy herds
nationwide. We are strongly recommending testing
before herds are moved between states, which should
both give us more testing information, and should
mitigate further state-to-state spread between herds.
The fate of the cows is another matter. So far, the USDA hasn’t issued orders to quarantine cattle, but it recommends minimizing their movement. Some states are restricting the import of cattle from states with infected herds.
The USDA has required poultry farmers to cull flocks infected with H5N1, leading to the loss of 85 million birds to date. Nothing this severe is being suggested for cows, but there are big concerns about what could happen if the virus in them spreads to poultry and leads to new infections in flocks.
Part of the problem, some experts said, is that the U.S.D.A. has long been in the position of both regulating and promoting the business of agriculture.
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. (...) 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.
Epidemiologists from the agency were ultimately unable to access a Texas dairy farm where a human was infected with the virus in March, they disclosed in attachments to the report published Friday by the New England Journal of Medicine. That prevented investigators from being able to investigate how workers might have been exposed to the virus on the farm.
That is because the dairy worker who came to a Texas field office for testing "did not disclose the name of their workplace," said Lara Anton, a spokesperson for the Texas Department of State Health Services.
They also were unable to collect follow-up samples from the dairy farm worker or their contacts, which could have revealed missed cases as well as tracking the virus and antibodies against it in the body after an infection.
The Centers for Disease Control and Prevention recommended this week that dairy and poultry farms with infected animals supply protective gear to workers in a bid to stave off human transmission of the H5N1 virus. The challenge now is making it happen.
The CDC has no legal authority to order those protective measures, and health officials in some of the nine states with reported outbreaks in cattle have had little luck getting farmers to take them up on offers of free personal protective equipment for their workers, even as the virus continues to spread.
During a briefing for reporters Wednesday, Vivien Dugan, director of the influenza division at the Centers for Disease Control and Prevention, said dairy worker vaccination might begin if any worrisome new changes are detected about the virus, such as changes in its genetic code.
From a human perspective, Worobey says, cows might be one of the worst possible animal reservoirs for influenza because of their sheer number and the degree to which humans interact with them. Culling poultry has curbed previous bird flu outbreaks, but Rasmussen says that isn’t a viable option for cattle. The animals are too valuable and, unlike birds, don’t seem to die from the infection.
But Gray says that there have been anecdotal reports of many more human cases. Leibler suspects that exposure of farm workers is widespread. “When you see symptomatic patients, that’s the tip of the iceberg,” she says. In the worst-case scenario, she says, the virus would spread undetected in several species for a long time, accumulating mutations that prime it for causing a pandemic in the future.
More could still be done to prevent further spread, scientists have suggested. “At milk processing plants, every incoming tanker load of milk is checked for adulterants, including antibiotics, and quality and safety standards,” veterinarian Kay Russo, who helped detect H5N1 at dairy farms for the first time, told Science. If these same standard were applied to H5N1, we would understand “the pervasiveness of this virus almost overnight.”
The bird flu outbreak in U.S. dairy cows is prompting development of new, next-generation mRNA vaccines—akin to COVID-19 shots—that are being tested in both animals and people.
Next month, the U.S. Agriculture Department is to begin testing a vaccine developed by University of Pennsylvania researchers by giving it to calves. The idea: If vaccinating cows protects dairy workers, that could mean fewer chances for the virus to jump into people and mutate in ways that could spur human-to-human spread.
He says there has been a lack of transparency around testing, and in many cases a lack of access for public health authorities. The setting of this outbreak – in dairy farms across a dozen or so states – adds a layer of bureaucracy that has further complicated the process. At times, public health officials from the CDC haven't been in sync with the Department of Agriculture, or with the state governments which must grant access for federal health officials to carry out testing on farms.
"We saw with swine flu in 2009, there was reticence to really address the risk on farms, and to sample farms — this has gotten better, but we always run into this because there is a very big commercial aspect in terms of export, and domestic consumption of meat and milk," he said.
The CDC reported May 22 that 40 people had been tested for highly pathogenic avian influenza nationally. The same day, Dr. Natasha Bagdasarian, Michigan's chief medical officer, told the Free Press that 35 Michigan farmworkers had undergone testing.
The means only five people who had been tested as of May 22 were from states other than Michigan. It also means the reach of the virus "is certainly more widespread" nationally than anyone currently knows, Monto said.
"The conclusions are pretty obvious when you hear things like that," said Monto. "If you don't look, you're not going to find it. What we need is to get serious about it in terms of how we handle surveillance because if you don't know it's there and don't have regulations in place ... it's going to spread even more."
At least three workers at U.S. dairy farms have tested positive this year after working directly with infected cows.
The latest case in Michigan developed respiratory symptoms, officials announced Thursday, which could make it easier for the virus to spread from person to person.
"Simply put, someone who's coughing may be more likely to transmit the virus than someone who has an eye infection like conjunctivitis," the CDC's Nirav Shah said Thursday.
In the human eye, however, the “bird” receptor is the one most frequently found, and this could explain why the virus in cows is causing eye infections in humans.
Lakdawala says she recently visited a parlor to observe the milking process. “It was eye-opening to me, and I, of course, got splattered on my face with milk because that’s what happens,” she says.
The cows were on a platform that put their udder roughly at eye level so humans could access it easily, she says. The first step in milking was “forestripping,” in which a worker very briefly milks the animal by hand to start lactation. When Lakdawala was watching this process, “these animals were just leaking,” she says, comparing the effect to that of water misters in a plant nursery.
In addition to providing every farmworker with PPE, Lakdawala believes the CDC should issue a “stay-at-farm” order for all cows “to get an assessment of what is happening and the extent of what has happened.” Tens of thousands of cows are transported across the country every week, she says.
As of April 24, 2024, USDA has confirmed H5N1 virus
detections on 33 dairy cattle premises in 8 states
(Kansas, Idaho, Michigan, New Mexico, North Carolina,
Ohio, South Dakota, Texas). USDA has also confirmed -
based on specific phylogenetic evidence and
epidemiological information - that 8 poultry premises in
5 states (Kansas, Michigan, Minnesota, New Mexico and
Texas) have also been infected with the same distinct
H5N1 virus genotype detected in dairy cattle.
During a briefing Thursday for journalists about the reports, STAT asked the USDA twice how many farms that have had positive cattle are still dealing with the virus. After all, some of the affected herds tested positive in late March. Mark Lyons, who is USDA’s national incident coordinator for the H5N1 response, did not come up with an answer, saying only that “94 herds are the ones we’ve detected since the start of this outbreak.”
Shortly after the briefing, USDA updated its list of affected herds, which now stands at 96 in 12 states.
Although it remains unclear whether an outbreak actually occurred, neither federal nor state officials investigated the matter for weeks. Only after inquiries by The Times did officials announce Tuesday that they would look into the report.
The delayed response, some experts say, suggests a disturbing lack of oversight on the part of government officials.
“I think that once everybody decided it wasn’t going to kill people and pasteurized milk and herds could get over it, then all that was left was to take these stopgap measures — voluntary reporting, voluntary testing, testing when going across state lines — that don’t look anything like a really serious effort to go ahead and stamp it out,” said Michael Payne, a researcher and outreach coordinator at the Western Institute for Food Safety and Security at UC Davis.
The Colorado Department of Public Health and Environment (CDPHE)
today reported that another worker culling poultry a second large layer
farm tested positive for H5N1 avian influenza in preliminary tests, just
days after it reported another case at the first farm, raising the
total number to seven. (...)The CDC also said it has uploaded a genetic sequence of the virus from one of the Colorado cullers to public databases. It is closely related to the B3.13 genotype found in recent poultry outbreaks and infected cattle herds. (...)
The virus primarily has avian genetic characteristics and doesn't have changes that increase its ability to infect or spread among humans. It has the same PB2 M631L mammalian adaptation marker seen in nearly all dairy cow sequences and in Michigan's first human case. It did not have the PB2 E627K mutation—linked in the past to adaptation in mammals—that was seen in an earlier human case from Texas.
As of the effective date of this Order, all CDPHE-licensed dairy cow farms in the state of Colorado must submit weekly bulk-tank samples for testing as set forth below.
In unpublished research, scientists at Colorado State University and Iowa State University who tested bulk milk tank samples found that the virus is detectable 14 to 16 days before farms saw a significant increase in symptoms like low appetite, lethargy, fever, and a dropoff in milk production.
That’s why the most important time to test is in the two to three weeks before clinical signs appear, said Keith Poulsen, a professor of large animal internal medicine at the University of Wisconsin-Madison and the director of the Wisconsin Veterinary Diagnostic Laboratory. “By the time you see them, you can’t do anything about it.”
And there are veterinary bills that go with sick animals. So yes, the dairy industry should want to address this, but they look at this right now largely as more of an inconvenience. The animals will get better. And in fact, if we look at what's happened in Colorado, they are now reporting 21 of the 65 farms that they have documented have now fully recovered, and the animals are back to health on that herd. And those herds are no longer under quarantine. So we do recognize for the milking industry that, in fact, this is one they just want to see in the rearview mirror. Now we in public health also have a concern about could this in fact lead to a situation where you have a cow, which is mammary gland, having both two six and two three receptors, both for human and avian viruses having the occurrence of a co-infection at the same time, meaning someone working at that dairy farm brings flu into the farm, infects the cow while milking and they in turn also have H5N1. Could we see a reassortment in that mammary gland of the cow? Yeah sure could.
I have done my checking, as have some others, and it's clear that the USDA does not have authority to mandate bulk tank testing throughout the country. In Colorado, for example, of those 65 farms I just mentioned, ten were picked up only after the state of Colorado mandated that the bulk tanks on the various farms be tested and found to be positive, when in fact they had not previously reported illness in their cattle. Wouldn't that be great if all at least the lower 48 states could do that? That hasn't happened, and USDA does not have the authority. Only the states could, and I don't see that occurring. In addition, the Health and Human Services, i.e. the CDC, do have emergency powers where they could actually mandate this to happen, but they would have to declare a national emergency first. And for them to do that. That means that they would have to put up 13 human infections, mild illnesses, and say, we have a national emergency. So that's not going to happen. So I think for the time being, we're stuck.
We’ve been told to be ready to do large-scale surveillance through bulk milk tank testing multiple times since May. For some reason or another, it has just never come to fruition.
This may be our last chance to halt bird flu in humans, and we are blowing it.