Category: Flu Virus

PHOTO PROVIDED Nadine Houck, a manager at the Penn State dairy barns, collects a sample of milk from a bulk tank for avian flu testing. The College of Agricultural Sciences announced it would support state surveillance efforts for highly pathogenic avian influenza in dairy cattle by testing Penn States herd for the virus.

UNIVERSITY PARK Animal health experts in Penn States College of Agricultural Sciences have announced that out of an abundance of caution they will test the Universitys dairy herd for highly pathogenic avian influenza, or HPAI, under a voluntary state testing program.

The announcement comes amidst an outbreak of bird flu that has affected dairy cattle in more than a dozen states since March. As of July 19, the virus had not been found in Pennsylvania dairy herds, according to the U.S. Department of Agriculture and state animal health authorities.

The Pennsylvania Department of Agriculture has encouraged all dairy farms in the state to enroll in its Lactating Dairy Cow Health Monitoring Program. The voluntary program is aimed at providing critical data on the status of dairy herds in Pennsylvania and detecting HPAI as quickly as possible should it arrive in the commonwealth.

The state herd monitoring program calls for conducting a weekly test of milk from a farm for three weeks, said extension veterinarian Ernest Hovingh, who is also a clinical professor of veterinary and biomedical sciences and director of Penn States Animal Diagnostic Laboratory. If all tests are negative and no clinical signs of the disease are observed, the herd is considered unaffected. At that point, weekly testing would continue, to ensure that the herd remains free of the virus.

He noted that unaffected herds are cleared for interstate transport of animals without any additional testing. For herds that do not participate in the monitoring program, Department of Agriculture regulations require testing of animals prior to movement across state lines.

Because Penn State does not move dairy cows across state lines, our herd has not been subjected to testing so far, Hovingh said. But participating in this program will allow us to determine if our herd is in fact HPAI-free, as strongly expected, and also will provide additional data to inform state and national surveillance efforts.

The chances of getting a positive test result are very remote, he added, but if that happens, Penn State and state officials will immediately investigate further.

Penn State attending veterinarian Jacob Werner, who oversees the health and well-being of all University livestock, said he and managers at the Penn State dairy barns have seen no signs to suggest that the virus is present in the herd, but it will be good to have testing data to confirm those observations.

We have a biosecurity plan in place to minimize the chances of bringing any diseases, including HPAI, into our herd, and we screen for sick cows regularly and consistently, Werner said. Drops in feed intake and milk production are two hallmark signs of most affected herds, and we monitor closely for those symptoms. We also dont import any animals into our herd, which appears to be the biggest risk factor for introducing HPAI infection to dairy herds.

Even in the unlikely event that the testing of Penn States herd brings back a positive result, Hovingh pointed out that in accordance with the U.S. Food and Drug Administrations Pasteurized Milk Ordinance, milk from sick cows does not leave the dairy and, therefore, does not enter the food supply.

In addition, all milk from Penn State cows is pasteurized before being sold for human consumption, he said. Numerous studies have shown that pasteurization inactivates pathogens such as avian flu viruses, and the FDA has confirmed that pasteurized milk and milk products are safe for human consumption.

Penn State will release the HPAI status of its dairy herd after the initial series of three weekly tests is completed, Hovingh said.

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Ten people in the state have contracted the virus so far, according to the Colorado Department of Public Health and Environment.

WELD COUNTY, Colo. More cases of avian flu in humans have been reported by Colorado health officials.

Three bird flu cases were reported at a second chicken farm in Weld County, the Colorado Department of Public Health and Environment (CDPHE) said in a release.

CDPHE said the cases were discovered after more testing was ordered for the poultry workers when another worker at the farm was confirmed to be positive. The workers who contracted the virus were culling birds that were positive for avian flu, CDPHE said.This is the second chicken farm in Weld County to have confirmed human cases of avian flu.

In all, 10 human cases of avian flu have been confirmed so far. Nine cases came from the two poultry farms, and one case came from a dairy farm.

The health department did not release information on the workers' conditions. In previous cases, the other positive patients had mild symptoms including pink eye and common respiratory infection symptoms, but none were hospitalized.

CDPHE announced they are launching a new online dashboard to track avian flu cases in humans. The dashboard will be updated by 4 p.m. on Tuesdays and Thursdays.

The dashboard will include:

The Colorado Department of Agriculture posts data on avian flu activity in poultry and dairy cattle weekly or as cases are confirmed.

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More human cases of avian flu reported in northern Colorado - 9News.com KUSA

A scientific team has confirmed the most feared scenario: the highly pathogenic avian influenza virus, which has been spreading through U.S. dairy farms for months, has managed to jump from cow to cow, and from cattle to cats and a raccoon. The researchers, from Cornell University, have issued a warning. Efficient and sustained mammal-to-mammal transmission is unprecedented. It is worrisome because it may cause the virus to adapt, enhancing its infectivity and transmissibility to other species, including people, the researchers note in their study, which was published urgently Wednesday in the journal Nature. The authors call for strict measures to prevent transmission to cows and to reduce the risk of a pandemic in humans.

The world is currently experiencing the biggest avian influenza crisis ever known. A subtype of the H5N1 virus, designated 2.3.4.4b, emerged in 2021 in wild birds and has since killed hundreds of millions of birds worldwide. The World Health Organization still considers the risk to the public to be low, although its records show that the H5N1 virus has jumped from birds to at least 889 people since 2003, killing 463 of them (52%). Scientists worst nightmare is that a virus with such lethality will mutate and become capable of human-to-human transmission, which has not happened so far.

Cornell researchers, led by Brazilian virologist Diego Diel, have observed that this subtype of the virus has a strong ability to infect udder cells and concentrate in milk, although it also appears in the lungs of cows. Scientists speculate that the pathogen may be transmitted via the respiratory or oral route, but they also suspect that it could enter through the teat orifice from contaminated soil or milking machines. As for the cats and the raccoon, the hypothesis is that they became infected by drinking contaminated milk. Two months ago, an experiment on mice showed that raw milk may contain viruses capable of transmitting the disease.

Virologist Elisa Prez is concerned about what is happening in the U.S., where 168 affected herds in 13 states have been identified since the first case was detected in a cow on March 25. It is very worrying, because it implies that cows constitute a new reservoir of avian influenza at least of this particular genotype and that they can act as a source of infection for other species, both birds and mammals. This is something that had never been observed before with this virus, since the only natural reservoir of avian influenza was birds, says the expert, from the Animal Health Research Center in Madrid. Infected cows may display symptoms such as reduced appetite, digestive disorders, respiratory problems and lower milk production. So far, there have only been outbreaks among cattle in the United States.

The nine farms tested in the study are in Texas, New Mexico, Ohio, and Kansas. They are outdoor farms, where wild birds have contact with dairy cows, both directly and indirectly, through contaminated feed or water. The first affected farms are on a route commonly used by migratory birds to cross North America.

On January 25, a scientific team found the B3.13 version of the 2.3.4.4b subtype of the H5N1 virus, the root of the unprecedented outbreaks in dairy cattle, in a Canadian goose in Wyoming. The analysis of the complete genome of the virus in cows has not detected mutations that favor the jump to humans.

Prez stresses that cows on a farm in Ohio became infected after the arrival of asymptomatic cattle from another facility in Texas. This confirms that apparently healthy cows can transmit the virus. That is, not all cows develop clinical symptomatology after infection. This has very important implications for surveillance systems, explains the virologist. With these data, it is clear that we should not only carry out passive surveillance (testing only samples from cows with symptoms), but it is also essential to include active surveillance programs, such as, for example, testing tank milk on all cattle farms, as will be the case in Colorado, one of the states most severely affected by avian influenza in cows.

American epidemiologist Maria van Kerkhove, director of the emerging diseases unit of the World Health Organization, declared two months ago that Covid-19 would not be the last pandemic we will deal with in our lifetimes. Diel points to H5N1 from his laboratory at Cornell University. It is difficult to predict which virus will be next but given the propensity of influenza viruses to cause pandemics, it is very important to keep a close eye on the H5N1 situation in dairy cattle, he explains to EL PAS.

The first outbreak that set off alarm bells worldwide occurred at a mink farm in Spain. In autumn 2022, dead seagulls and gannets appeared on Galician beaches. In early October, American mink began to die of hemorrhagic pneumonia at a fur farm in Carral, outside A Corua. Mortality in the outbreak exceeded 4% in just seven days. A study led by biologist Montserrat Agero, of the Ministry of Agricultures Central Veterinary Laboratory, suggested in January 2023 that the avian flu virus had jumped from wild birds to mink, mutated on the farm, and been transmitted from mammal to mammal. Early last year, the mass death of sea lions from bird flu in Peru suggested that the virus might be jumping between mammals in the wild. Dutch veterinarian Thijs Kuiken, of the Erasmus University Medical Center in Rotterdam, then posed a question in EL PAS: If it occurs in minks and sea lions, why wont it occur in humans?

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Study confirms deadly bird flu is being transmitted between cows - EL PAS USA

Of all the news about bird flu, this month has brought some of the most concerning yet. Six people working on a chicken farm in Colorado have tested positive for the virusthe biggest human outbreak detected in the U.S. The countrys tally is now up to 11 since 2022, but thats almost certainly a significant undercount considering the lack of routine testing.

Since the current strain of bird flu, known as highly pathogenic avian influenza H5N1, began spreading around the world in late 2021, it has become something like a super virus in its spread among animals, Richard Webby, an influenza expert at St. Jude Childrens Research Hospital in Memphis, told me. Wild birds have been decimated, as have poultry farms: The virus has been detected in more than 100 million birds in 48 states. H5N1 has been around for longer than 25 years, but only recently has it regularly jumped to mammals, infecting cats, sea lions, and bears. In March, it was detected for the first time in American cattle and, since then, has already spread to 163 herds in 13 states.

All of that would be worrying enough without reports of people also falling sick. Everyone who has tested positive in the U.S. has worked closely with farm animals, but each additional case makes the prospect of another human pandemic feel more real. Thats absolutely the worst-case scenario, Webby said. Its a possibility, although not the likeliest one. For now, the virus seems poised to continue its current trajectory: circulating among wild birds, wreaking havoc on poultry farms, and spreading among cattle herds. That outcome wouldnt be as catastrophic as a pandemic. But its still not one to look forward to.

Even with the spate of farmworker infections, the threat of bird flu to humans is, at the moment, considered low. Researchers are keeping an eye out for two red flags. The bigger one would be the viruss ability to spread between people. All of the people who have tested positive in the U.S. were infected by exposure to sick cows or poultry, and they have not seemed to pass the virus along to anyone else. Symptoms have generally been mild, including respiratory issues, though several people have developed serious cases of conjunctivitis, or pink eye. (No one in the U.S., or globally, has died from this variant of H5N1.) There is no evidence at this point that this virus is going human to human, and therefore it really does not pose a threat to public health, Jenna Guthmiller, an immunologist at the University of Colorado Anschutz School of Medicine, told me.

The second warning sign is how the virus itself is changing. So far, H5N1 isnt very good at getting into human cells and then replicating inside them, abilities that would enable the viruss spread among people. But that may be changing. In a lab study, virus particles from infected cows showed signs that they were capable of binding to human receptors in the upper respiratory tract.

The current strain of H5N1 has already mutated to infect mammals, and a few genetic changes could be all it takes for the virus to spread more efficiently to humansor, worse, between them. Were at the highest risk of the virus since the early 2000s, when a different strain of H5N1 led to numerous deadly human infections in East and Southeast Asia, Webby said. Not because the virus itself is necessarily more infectious but because it is spreading among so many different animals, and especially mammalsgiving it more opportunities than ever to find a way to replicate in humans. But, again, despite all that transmissionall those chances for the virus to mutate into something that can reliably sicken humansit hasnt yet. That could absolutely continue to be the norm, David Topham, a flu expert at the University of Rochester Medical Center, told me.

The status quo is still pretty troubling. New cases of bird flu keep popping up in herds across the country, raising fears that it might never be eradicated from cattle. The most likely scenario, Webby said, is that this virus will become endemic in birds and dairy cowsa constant presence, regularly causing outbreaks. Right now, infections in poultry tend to align with the migration of wild birds; if cows are constantly infected, chicken outbreaks could become more frequent.

Nothing about endemicity would be good for humans. The consequences would be diminished, but not eliminated. Farmworkers may continue to periodically fall sick, Guthmiller said. The cost of regular animal outbreaks would be exorbitant. The USDA has already allocated more than $2 billion to address surges among poultry and livestock, which includes compensating farmers for animals that have been killed and eggs that have been destroyed to quell the spread.

If the virus continues to regularly sicken cows, it will have even more opportunities to mutate in a way that could allow it to more easily infect humans. In infected cows, virus particles are mostly found in their udders; the virus is thought to spread between the animals through contaminated milking equipment. Research released last week, which has not yet been peer reviewed, indicates that cows can be infected by aerosolized virus; if they can spread the virus through their exhalations and sneezes, they could become infected merely by breathing the same air.

H5N1 is restlessit will continue trying to infect new hosts. Given enough opportunities to mutate, the virus will do so. Its like playing the lottery, Topham said. Were giving this virus a lot of tickets. H5N1 may also be able to combine with flu viruses from different animals. If cows, chickens, and other animalssay, pigs, which arent affected by the current outbreakon the same farm all have different versions of the flu, thats your mixing vessel right there, Topham said. The H1N1 virus that caused the 2009 swine-flu outbreak, for example, was a mix of flu viruses from pigs, humans, and birds.

There is one other possible futurethe best-case scenario, which unfortunately is also the least likely. The virus possibly could disappear, Webby said. This would partly depend on eradicating it from cows, which he believes is plausible with human intervention and herd immunity. But eliminating the virus in birdsthe main animals that get bird flu and spread itis largely out of human control. H5N1 is particularly lethal in birds, with a mortality rate of up to 100 percent for some species; if it somehow kills enough of them, Guthmiller said, it very well could just fizzle out. Dumb luck, as Webby put it, might still prevail.

But a supercharged bird virus with a taste for infecting mammals is not the kind of thing that should be left up to chance. It is fortunate that only 11 farmworkers have been infectedas far as we know. Tools to curtail the spread of bird flu are available, but theyre not being used, or used appropriately. Personal protective equipment is helpful when worn correctly, but doing so isnt feasible when it involves wearing respirators and Tyvek suits in temperatures that reach 104 degrees Fahrenheit. Unlike many other countries, the U.S. does not vaccinate chickens against H5N1, in part because its expensive to do. And cost is also why only 60 farmworkers have been tested for bird flu, giving an imperfect window into the viruss spread. Its going to be a lot more costly to deal with another pandemic than to deal with immunizing our farms, Topham said.

Americas response has been painfully shortsighted, and the country is paying the price: Had bird flu been kept in check earlier, it might never have made it into cows, and might never have developed the mutations that allow it to flirt so closely with human-to-human transmission. At this point, bird flus future has no good optionsonly one thats bad, another thats abysmal, and one that relies on nothing but dumb luck.

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There Are No Good Options Left With Bird Flu - The Atlantic

The Colorado Department of Agriculture this week stepped up efforts to stop a runaway outbreak of bird flu cases on dairy farms by issuing an order requiring testing for the virus on all commercial cow dairies licensed by the state.

But, separately, new information about the bird flu virus that infected a Colorado farmworker provides reassuring evidence that the virus remains a low risk to human health.

The state has seen at least 51 cases of bird flu on dairy farms since April, meaning nearly half of all commercial dairies in Colorado have been affected. Of those cases, 30 have happened in the past 30 days.

Colorados outbreak continues to surge even as others have dwindled nationwide no other state has seen more than four cases in the past 30 days, and some major dairy-producing states like Wisconsin and California have never reported any cases.

In issuing the order, state veterinarian Dr. Maggie Baldwin said the virus, while not causing deaths of many cattle, has still been a devastating disruption to Colorados dairy industry resulting in quarantines and loss of milk production.

We have been navigating this challenging, novel outbreak of HPAI in dairy operations for nearly three months in Colorado and have not been able to curb the spread of disease at this point, Baldwin said in a statement, using a shorthand term for the virus, which is also known as highly pathogenic avian influenza.

The order does not apply to farms that produce raw milk, which are not regulated by the state. Pasteurization kills the virus in milk sold in stores, but raw milk is unpasteurized, meaning there is the potential for it to contain live virus.

Baldwin noted that, as the dairy outbreaks rage on, they are also generating spillover cases in other animals. Most notably, Colorado has begun seeing infections again in commercial poultry operations.

There have been two major, confirmed outbreaks at egg-laying operations in Weld County, while a third, suspected outbreak is also under investigation. Those outbreaks have resulted in the culling of more than 3.2 million chickens just in July, according to the Department of Agriculture.

Colorado has now seen 33 commercial poultry flocks affected since 2022, with more than 6.3 million domestic birds culled.

Then theres the human toll. One of those poultry outbreaks led to an unprecedented cluster of cases among workers who were doing the culling. Six workers were confirmed positive for bird flu, though their symptoms were relatively mild and none required hospitalization.

Meanwhile, the Colorado Department of Public Health and Environment announced Thursday that it has identified three new human cases of bird flu these tied to culling operations at a different poultry farm. The workers, likewise, have mild symptoms and have been offered antiviral drugs for treatment.

Including the new cases, the state has now identified 11 out of the 14 human cases nationwide since 2022, placing Colorado at the center of the nations bird flu epidemic. And the burst of human infections in Colorado has raised questions about whether the flu virus has mutated to make it more capable of infecting people.

But a new CDC analysis eases those concerns. The CDC took a virus sample from one of the Colorado poultry workers and sequenced its genome.

Among the findings:

So, to recap: Nothing about the Colorado case suggests the bird flu virus has become better able to infect people, hurt people or spread to other people. The CDC said the analysis supports CDCs conclusion that the human health risk currently remains low.

The CDC also reported some more good news last week: Blood tests of Michigan dairy workers were boring.

Michigans public health department conducted what is known as a seroprevalence study of workers with known exposures to infected cows. The goal was to see if workers who showed no symptoms of bird flu actually had antibodies against the virus. If they did, it would suggest that they had been silently infected and that human cases might be more common than known.

Instead, the results from every nonsymptomatic worker tested came back clean no antibodies against bird flu.

This is an important finding, the CDC wrote in a weekly update, because it suggests that asymptomatic infections in people are not occurring.

That means the risk remains primarily to farmworkers who have direct contact with infected animals. And that puts the focus on efforts to provide information to farms and to ensure workers have access to and are able to wear protective equipment.

Ongoing cooperation is key to supporting workers health and safety, protecting animal health and welfare, and minimizing the spread of the virus, Kate Greenberg, Colorados commissioner of agriculture, said in a statement.

Based on facts, either observed and verified directly by the reporter, or reported and verified from knowledgeable sources.

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Colorado expands testing for bird flu at dairy farms as state hits 30 cases in 30 days - The Colorado Sun

Just how deadly is the H5N1 avian flu? The virus, which is currently sweeping through U.S. dairy herds, rarely jumps to human beings, at least for now. But when it does the consequences can be grave: The World Health Organization reports that 52 percent of people known to be infected with H5N1 have died from the disease.

The figure has been widely cited in academic papers, public health communications, and media reports, where it can provoke apocalyptic visions. Bird flu pandemic could be 100 times worse than COVID, claimed one New York Post headline. An article in The Guardian leads with the WHOs enormous concern about the spread of H5N1, which, according to one lead scientist quoted, has an extraordinarily high human mortality rate.

The actual picture, while still alarming, is more complicated. The WHOs H5N1 mortality figure, an average of wildly different death rates from past outbreaks, doesnt factor in mild cases that went undetected. Even less certain is how lethal H5N1 would be if it evolves to spread not just from animals to humans, but also from person to person.

That genetic twist would likely diminish H5N1s virulence, experts predict, but no one can say how much less deadly it might become. And even a virus that kills far fewer than 52 percent of people would be devastating: As the world saw with the Covid-19 pandemic, even a death rate of 1 to 2 percent can be catastrophic.

But answering how lethal an H5N1 pandemic might be is no easy feat. A dive into that question reveals the ongoing challenges and, some experts say, failures of tracking the virus. And it offers a glimpse at the difficulty of communicating the risks and unknowns about an emerging pathogen.

Since the first human outbreak of H5N1 in Hong Kong in 1997, the disease has cropped up sporadically around the world, almost entirely infecting people who worked directly with poultry. Between Jan. 1, 2003 and May 3, 2024, the World Health Organization recorded 889 cases of H5N1 and 463 deaths. Dividing the total deaths by the number of cases results in what epidemiologists call a case fatality rate, or CFR, of 52 percent.

But CFRs are notoriously uncertain. The fundamental problem is that a case is not a tightly defined scientific concept, said Harvard epidemiologist Marc Lipsitch. These numbers are something we have to use because we dont have something better, but people in the business are aware that they are potentially deceptive.

When and where researchers look for cases can heavily bias CFRs. A virus that produces mild, undetected infections in 998 people, sends two people to the hospital, and then kills one of the hospitalized patients will have a CFR of 50 percent if public health authorities only manage to detect those two serious cases. But the true fatality rate would be one person in 1,000, or 0.1 percent.

During a 2003 H5N1 outbreak in Vietnam, a relative watches over a family member who has contracted the disease. Between Jan. 1, 2003 and May 3, 2024, the World Health Organization recorded 889 cases of H5N1 and 463 deaths. Visual: Paula Bronstein/Getty Images

Accurate CFRs are critically important in an outbreak because marshalling a public health response depends on understanding the diseases severity. For example, when H1N1, also known as swine flu, emerged in Mexico in the spring of 2009, tens of thousands of mild cases went undetected, causing health authorities to overestimate the severity of the disease. In a study published later that year, Lipsitch and an international group of researchers from organizations including the Centers for Disease Control and Prevention estimated that the actual case count among Mexican residents that spring was about 100 times higher than officially reported.

On the flip side, though, if researchers overlook fatal cases they will underestimate the lethality of a virus. For instance, research suggests that health authorities initially undercounted deaths in a 2003 SARS outbreak in Hong Kong because they didnt follow patients long enough to record everyone who died of the disease.

Like many experts, Peter Palese, a microbiologist at the Icahn School of Medicine at Mount Sinai in New York, thinks that the CFR of 52 percent for H5N1 calculated by the WHO likely overestimates the diseases severity. To meet the WHOs definition of an H5N1 case, the person must have had a fever and tested positive for the virus in a lab with the technical capacity to follow WHO protocols. Because many of the outbreaks have been in rural areas without sufficient testing capabilities, the case count is drawn almost exclusively from patients who were sick enough to be hospitalized. Meanwhile, said Palese, many milder infections likely went undetected, although the exact number of those silent infections is unknown.

It is not completely clear whether these high fatality rates are real, said Palese.

These numbers are something we have to use because we dont have something better, but people in the business are aware that they are potentially deceptive.

Outbreaks are like an iceberg where serious infections are immediately visible, but the larger numbers of mild infections are out of sight below the water line, said Malik Peiris, a virologist at the University of Hong Kong with extensive experience with H5N1. One of the best ways to get a more accurate case count, he said, is to test community members blood for antibodies against H5N1, which would indicate a previous infection: That gives you a much more accurate picture of the bottom of the iceberg.

Researchers have conducted dozens of such studies. But results from that research, said Peiris, are a bit mixed and somewhat confusing. While antibody studies of some H5N1 outbreaks find evidence of widespread mild infections, studies of other H5N1 outbreaks do not, even among people who worked closely with infected birds. Peiris described the disparity as rather puzzling.

Its possible, said Peiris, that antibody tests miss some cases. Type A influenza viruses such as H5N1 are characterized by the combination of two proteins on their surface: hemagglutinin, which can be one of 18 types numbered H1 to H18, and neuraminidase, numbered N1 to N11. Compared to the H1 and H3 proteins in the influenza A viruses responsible for seasonal flu, H5 proteins trigger a weaker response from the immune system, said Peiris: People may be getting mildly infected, but its not enough to elicit an antibody response.

Peiris and other experts described the current H5N1 outbreak in dairy farms as a prime opportunity to investigate how and where H5N1 is spreading as well as how we might contain it. But in many areas, farmers who are worried about the threat to their livelihood wont allow officials on site to test workers or animals.

As of July 18, H5N1 has been identified in 163 herds of dairy cattle in 13 states. But wastewater surveillance data showing spikes of Influenza A outside of flu season in some regions suggests that H5N1 could be circulating more widely, said epidemiologist Michael Osterholm, who heads the University of Minnesotas Center for Infectious Disease Research and Policy. Weve already missed a big chunk of potential worker infections, he said. Still, even now, antibody testing would give us a darn good picture of the number of human cases.

Thats the kind of thing we really need to get a handle on, Osterholm said. The absence of evidence is not evidence of absence.

Between March 2024 and now, H5N1 surveillance has entailed monitoring about 1,570 people who have been exposed to infected animals and testing at least 62 people, CDC spokesperson Jasmine Reed wrote in an email to Undark.

It is not completely clear whether these high fatality rates are real.

There have only been 11 reported cases of bird flu in humans in the U.S. since 2022, according to the CDC, with just five of those confirmed as H5N1. All cases have involved farmworkers who worked with infected animals. The agency is also providing technical assistance on an antibody testing by the Michigan Department of Health and Human Services that is looking for asymptomatic infections among people who worked with sick cows.

But, like many experts, Osterholm is worried that testing is wildly insufficient. More than 9 million cows produce milk across all 50 states, according to the U.S. Department of Agriculture. And the dairy farm industry employs more than 100,000 people.

While Michigan appears to be ground zero for the current outbreak, Osterholm said, I dont believe for a second thats really true. Michigans agriculture and health departments have just been more proactive about surveillance and testing, he said: Im convinced, quite honestly, that if they can get on more farms in more states, youll see this is much more widespread.

Accurately assessing the lethality and spread of H5N1 is crucial to predicting what could happen next.

For now, H5N1 has proven deadly, but still hard for humans to catch. If this were to become a pandemic virus, Osterholm said, it would have to go through major changes.

What those changes would mean for the virus lethality, though, is unclear.

H5N1 could develop the capability for person-to-person transmission in a few ways. In the process of replicating, viruses could acquire random mutations that make them better suited to a human host. In addition, different types of viruses can swap genes through a process called reassortment. So, if a human or other animal were infected with both a typical human flu virus and H5N1, those viruses could generate a new strain that was both deadly and easily transmitted.

Only a small set of avian influenza viruses have evolved to infect mammals, said Thomas Friedrich, a University of Wisconsin virologist who studies the evolution of pandemic viruses. To infect a host, viruses latch on to receptors on the surface of cells, Friedrich explained. The receptors H5N1 binds to in birds are configured differently from most of those in humans. People only have bird-type receptors deep in the lungs, said Friedrich, where infection is associated with severe disease.

That can help explain both why human infections with H5N1 viruses have tended to be very severe, he said. And why those viruses that infect those unfortunate humans have a hard time getting from that human to another one. To efficiently spread from person to person, the virus would need the ability to attach to human-type receptors in the upper respiratory tract. Once it takes hold there, talking, sneezing, coughing, and even breathing will then spew it into the world.

While it would probably only take a couple of genetic changes to get to that point, said Friedrich, we dont find a whole lot of evidence that bird viruses infecting humans are evolving toward the ability to bind those upper respiratory tract cells.

One theory for why, so far, H5N1 has not evolved to infect the upper respiratory tract in people is that the virus so successfully survives and replicates in the lower lungs that it outcompetes any mutations, said Friedrich. Data from his lab and others suggest that mutations that could bind with human-type receptors die off before taking hold.

Im convinced, quite honestly, that if they can get on more farms in more states, youll see this is much more widespread.

But that could change, he said, when the virus infects a species with both human-style and bird-style receptors. For example, researchers have pinpointed the start of the 2009 H1N1 pandemic to pigs, which can be infected with both human and bird flu. And a recent study in preprint that has not yet been peer-reviewed finds that cow udders can also contain both types of receptors and so could potentially become a mixing vessel for bird and flu viruses.

A new study published in the journal Nature suggests that may already be happening. A team of researchers from the U.S. and Japan found that H5N1 virus isolated from the milk of infected cows could bind with both human and bird receptors. Those results are controversial, however, as other researchers whove studied current strains of the virus concluded that it hasnt become more specific to humans.

In the last two years, H5N1 has spread to nonhuman mammals such as foxes, skunks, cats, mice, and marine mammals perhaps both because they are encountering more infected birds and because the virus has become better suited to mammalian hosts, said Friedrich. If the virus further evolved to infect the upper respiratory tract, rather than the lower lungs, of humans, researchers speculate that could make it less lethal, he said: But there is no hard-and-fast rule that viruses dont evolve to kill their host.

Like many researchers, Peiris is concerned that if H5N1 becomes a pandemic virus, the mortality rate would be much higher than that of Covid-19. He pointed to a recent CDC study showing that an H5N1 virus isolated from a person infected in a recent outbreak was lethal to ferrets, which he said are the best animal model for human severity and transmission.

An H5N1 pandemic would have catastrophic consequences, he said. I have no doubt about that.

There is one hopeful note. In early 2024, Peiris and his colleagues published a study suggesting that previous infection with the H1N1 swine flu may provide some protection against H5N1. In testing blood samples collected from a random sample of 63 adult blood donors, the researchers found that antibodies resulting from a previous infection of swine flu also reacted to the N1 protein in H5N1. While that immune response wouldnt block an infection entirely, it might mitigate its severity, said Peiris. The team is now studying that possibility in animal models.

For now, many public health experts remain frustrated by the lack of clear data on H5N1 especially following similar problems in the early days of the Covid-19 pandemic.

Public health authorities should be doing far more testing for evidence of H5N1 in agricultural workers, said Jennifer Nuzzo, who directs the Pandemic Center at the Brown University School of Public Health. But even if they did test more, said Nuzzo, there is a need for standardized protocols.

This is one of those things that we know we need to do, said Nuzzo, who spoke with Undark in June. Since then, the CDC has published such protocols for antibody testing, which would make studies easier to compare because researchers have used different methods in previous outbreaks. That has been an issue in the past, when, Nuzzo said, we jumped to very consequential conclusions based on these data that could very well be the product of a very biased study design.

While Nuzzo would like to see more farmworkers tested regularly, she acknowledges that its a hard-to-reach population. Farm owners arent always cooperative. And the workers, many of whom are undocumented, may also be reluctant to submit to testing that they view as a threat to their tenuous lives in the U.S. In the meantime, Nuzzo is adamant that farmworkers should be offered vaccination against the virus.

Amid the uncertainty, some public health experts suggest, the public conversation about H5N1 has become disconcertingly contradictory, with reassuring messages that risks are low juxtaposed against warnings of a brewing pandemic.

Communication about the threat of H5N1 often lacks nuance and perspective, said Osterholm. Figures like a 52 percent death rate, he said, do little to capture the profound unknowns about an ever-changing virus. At the same time, statements saying that theres little reason for the public to worry about H5N1 like recent pronouncements from the CDC appear to downplay the threat. For example, Nuzzo emphasized that the risk to farmworkers is not low.

Its true that the virus currently poses little risk to the general public, said Osterholm. But all that could change tonight.

Amid the uncertainty, some public health experts suggest, the public conversation about H5N1 has become disconcertingly contradictory.

Many health authorities view the flood of alarming and conflicting information on Covid-19 as an example of how not to communicate during a pandemic. Public guidance from the CDC was confusing and overwhelming, according to a 2022 internal review.

A common mistake was oversimplifying information, stripping out essential details and glossing over unknowns, said Nuzzo. That undermined peoples trust in advice that changed along with the evolving scientific information. You have to take people on the journey with you, she said. Because if you put a fairly high-consequence conclusion in front of them and dont kind of have anything to back it up, I think its natural that people are going to feel skepticism.

The public is much smarter than theyre given credit for, said Nuzzo, And I think people are hungrier for more information, not less.

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How to Pinpoint the H5N1 Mortality Rate in Humans - Undark Magazine

Nine farmworkers at two egg farms in Colorado have contracted mild cases of bird flu since mid-July while killing and disposing of millions of infected chickens, said public health officials on Thursday. These preliminary results again underscore the risk of exposure to infected animals, said theCenters for Disease Control(CDC), which added that the risk to the general population remains low.

TheColorado Department of Public Healthsaid that approximately 118 people have been tested for the avian flu virus and 10 cases have been confirmed nine on poultry farms since July 12 and one on a dairy farm in May. The national total, which includes three workers on dairy farms in Michigan and Texas, is 13 since April. In addition, a Colorado correctional inmate was infected with the H5N1 virus while culling an infected chicken flock in 2022.

All of the infected poultry workers were employed on egg farms in Weld County, northeast of Boulder six on one farm and three on the other. The CDC and the Colorado Department of Public Health jointly announced confirmation of the outbreak among workers on the second farm.

The three confirmed cases occurred in people who were working directly with infected poultry at a commercial egg layer operation that had reported an outbreak of H5 bird flu among poultry, said the CDC. All three people have mild illness and have been offered the antiviral drug oseltamivir for treatment. State and local officials continue to monitor poultry workers on farms with infected poultry.

According to the CDC, The risk to the general public from H5N1 [avian flu virus] remains low. Genetic tests show that the virus has not changed in ways that would make it more communicable, it said, and there have been no signs of unexpected increases in flu activity in Colorado or the rest of the country.

Highly pathogenic avian influenza has killed nearly 101 million birds in domestic flocks in 48 states since the disease appeared in the United States in February 2022. Some 172 dairy herds in 13 states have been diagnosed with H5N1 infections since late March. Fifty of them are in Colorado.

For weeks, the CDC has said people working with infected or potentially infected livestock should wear protective gear. For jobs like culling infected flocks, workers should wear water-resistant coveralls, masks, goggles, gloves, and boots, it says. Officials have acknowledged that it is difficult to assure compliance during prolonged physical labor in hot weather.

Historically, most human cases of bird flu infection have happened in people who are not wearing recommended personal protective equipment, said the CDC. Investigators will ask about the use of protective equipment on the Colorado farms, it said.

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Bird flu spreads among Colorado farmworkers, with nine infected in two weeks - Successful Farming

In a recent study published in the journal Nature, scientists in the United States report the spillover of the highly pathogenic avian influenza (HPAI) H5N1 virus in cattle across several United States (US) regions. They further document the detailed symptomatic outcomes of the resulting disease in these bovine populations. Finally, they use a multidisciplinary approach incorporating epidemiological and genomic analyses to highlight that the virus's evolution confers the ability to allow for not only cow-to-cow transmission but also efficient multidirectional interspecies spillover, infecting birds, domestic cats, and even a raccoon in proximity to diseased cattle.

Study: Spillover of highly pathogenic avian influenza H5N1 virus to dairy cattle. Image Credit:Studio Romantic/ Shutterstock

Influenza A virus (IAV) H5Nx is a highly pathogenic avian influenza (HPAI) virus causing widespread respiratory illness and subsequent death in bird populations across Africa, Asia, Europe, and most recently North America. First discovered in China in 1996, the colloquially termed 'bird flu' has since evolved into eight clades and three neuraminidase subtypes, with the H5N1 subtype 2.3.4.4b being its most prevalent and epidemiologically relevant representative.

HPAI H5N1 is alarming, given its potential for spillover (cross-species infectivity). It has been reported to be transmitted from infected poultry populations into wild birds (2002), mammals (domesticated and wild), and even humans (2003). The World Health Organization (WHO) documented 860 human infections and more than 430 deaths since 2003 (fatality rate ~52.8%).

The virus poses significant threats to ecology, economy, and public health, having claimed more than 90 million bird lives in the United States (US) alone. The most recent H5N1-associated morbidity event was that of dairy cattle across Texas (TX), New Mexico (NM), Kansas (KS), and Ohio (OH) between January and March 2024. Understanding the epidemiological and genomic underpinnings of this event may allow researchers to elucidate the etiology (origin) of the disease and prepare for future outbreaks.

Influenza A Virus (H5N1/Bird Flu) Influenza A (H5N1/bird flu) virus particles (round and rod-shaped; red and yellow). Creative composition and colorization/effects by NIAID; transmission electron micrograph imagery is courtesy CDC. Scale has been modified/not to scale. Credit: CDC and NIAID

The present study documents the January-to-March 2024 morbidity event in American cattle across TX and its neighboring states. It uses a detailed multidisciplinary approach incorporating clinical, epidemiological, and phylogenomic investigations to elucidate the pathophysiology of the virus and the genetic underpinnings of its spillover potential.

Researchers first obtained samples for the clinic-epidemiological evaluation from nine farms across affected states TX (5 farms), NM (2), KS (1), and OH (1). Notably, the singular farm in OH was affected following the introduction of cattle (assumed to be healthy) from the first affected TX farm.

Data collection comprised nasal swabs, milk, blood buffy coats, and serum (n = 331). These samples were subjected to real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) and viral metagenomic sequencing. Additionally, tissue from birds (great-tailed grackles, rock pigeons) and mammals (cats and raccoons) found dead at infected farms were subjected to rRT-PCR analysis.

Virus-shedding investigations were conducted to elucidate the source and duration of viral transmissions following initial infections. Excised tissues from cows, dead birds, and mammals were subjected to histological examinations. Finally, phylogenomic analyses were conducted to isolate the etiological source of the viral strain and the genetic underpinnings of its substantial spillover.

Clinical-epidemiological investigations revealed multiple disease symptoms in cattle, notably decreased feed intake, mild respiratory distress, reduced rumination time, lethargy, dehydration, abnormal feces, and abnormal milk production (20-100% reduction in quantity, yellow color, and thick consistency). Symptoms persisted for 5-14 days. However, milk production remained reduced for up to four weeks.

All investigated rRT-PCR samples positively detected viral load, but virus shedding was the highest and most frequently detected in milk samples and mammary gland tissue. Notably, while virus shedding duration investigations detected viral loads in milk samples on days 3, 16, and 31 post-infection, infectious virus shedding was only observed on day 3.

"Histological examination of tissues from affected dairy cows revealed marked changes consistingof neutrophilic and lymphoplasmacytic mastitis with prominent effacement of tubuloacinar glandarchitecture which were filled with neutrophils admixed with cellular debris in multiple lobules inthe mammary gland. The most pronounced histological changes in the cat tissues consisted of mild to moderate multi-focal lymphohistiocytic meningoencephalitis with multifocal areas ofparenchymal and neuronal necrosis."

Phylogenomic analysis revealed that all recovered viral sequences aligned with a novel monophyletic reassorted substrain of H5N1 termed B3.13, first discovered in a Canada goose in Wyoming (25 January 2024). This lineage was most closely related to a sequence obtained from a deceased skunk in NM (23 February 2024). The similarity between viral genomes from investigated farms highlights circulation and cross-infectivity between their inhabitants, likely due to the transportation and introduction of animals between these farms.

The present study highlights the potential of H5N1 viral spillover and cross-infectivity in both avian and mammalian hosts across farms in the US. The mammary gland was highlighted as the region with the highest viral replication, with infected milk representing the most likely transmission route. The novel substrain (B3.13) identified herein is alarming given its spillover potential (to domestic and wild bird populations and even other mammals cats, and raccoons).

While no human infections were reported from under-study farms, mild infections were reported during the study duration from other farms near the study area, highlighting the virus's zoonotic potential and the potential for a human pandemic.

According to guidelines from the CDC, it is crucial to wear the recommended personal protective equipment (PPE) when working directly or closely with sick or dead animals, such as animal feces, litter, raw milk, and other materials that might have the virus. The recommended PPE includes fluid-resistant coveralls, a waterproof apron, a NIOSH-approved respirator (e.g., N95), properly-fitted unvented or indirectly vented safety goggles or a face shield, head cover or hair cover, gloves, and boots.

Proper procedures for putting on and removing PPE, such as washing hands before and after using PPE and disinfecting reusable PPE after every use, are essential. Additionally, it is advised to shower at the end of the work shift, leave all contaminated clothing and equipment at work, and watch for symptoms of illness for ten days after working with potentially sick animals or materials.

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Alarming spread of H5N1 bird flu in US dairy cattle reveals cross-species transmission dangers - News-Medical.Net

A new paper challenged two ideas about how the H5N1 bird flu behaves in cattle: that it always produces mild illness, and that asymptomatic animals don't spread disease.

Instead, the paper showed that cattle mortality was twice as high during outbreaks on two of the nine farms assessed, and almost a third of nasal swabs in asymptomatic animals were positive for the virus, as were half of urine samples.

The findings underscore "the need for robust measures to prevent and control the infection and further spread of HPAI [highly pathogenic avian influenza] H5N1 in dairy cattle," Kiril Dimitrov, DVM, PhD, of Texas A&M Veterinary Medical Diagnostic Laboratory in College Station, and co-authors wrote in Nature. "This would reduce the risk of the virus adapting in this new mammalian host species, thereby decreasing the pandemic risk to humans."

Dimitrov and colleagues studied nine farms -- five in Texas, two in New Mexico, one in Kansas, and one in Ohio -- that had outbreaks from February 11 to March 19.

The New York Times reported that 99 cows died during a 3-week outbreak on the Ohio farm, which is twice the normal mortality rate. The other increased mortality event occurred on a Texas farm, according to the paper.

The researchers found evidence of subclinical infection in some cows, with viral RNA detected in six of 19 nasal swabs and four of eight urine samples. Interestingly, animals with clinical illness shed virus at a lower frequency in nasal swabs and urine, they noted.

That has implications for the risk of spreading the virus between farms, as the researchers said epidemiologic and genomic data showed cow-to-cow transmission after apparently healthy cows from a Texas farm were transported to a farm in Ohio.

It's "possible that the virus infects through respiratory and/or oral routes replicating at low levels in the upper respiratory tract, from where it could disseminate to other organs via a short and low-level viremia," Dimitrov and colleagues wrote, notably to the mammary glands.

Indeed, the paper confirmed that H5N1 has high tropism for mammary gland tissue in cows, which is "consistent with high expression of sialic acid receptors with an alpha 2,3 (avian-like receptor) and alpha 2,6 (human-like receptor) galactose linkage in these cells."

It also confirmed prior reports about key symptoms of the disease in cattle, including "decreased feed intake, decreased rumination time, mild respiratory signs (clear nasal discharge, increased respiratory rate, and labored breathing), lethargy, dehydration, dry/tacky feces or diarrhea, and milk with abnormal yellowish colostrum-like color, thick and sometimes curdled consistency."

Cattle often had an abrupt drop in milk production that could last for about a month, the researchers pointed out, but they generally recovered from their illness in 5 to 14 days, returning to their pre-outbreak health status.

The virus spread widely among other animals on or near the farm, including to cats, raccoons, and wild birds, which was confirmed by genomic analysis. "These observations highlight complex pathways underlying the introduction and spread of HPAI H5N1 in dairy farms, underscoring the need for efficient biosecurity practices and enhanced surveillance efforts in affected and non-affected farms," Dimitrov and co-authors concluded.

"The spillover of HPAI H5N1 into dairy cattle and evidence for efficient and sustained mammal-to-mammal transmission are unprecedented," they wrote. "This efficient transmission is concerning as it can lead to the adaptation of the virus, potentially enhancing its infectivity and transmissibility in other species, including humans."

Kristina Fiore leads MedPages enterprise & investigative reporting team. Shes been a medical journalist for more than a decade and her work has been recognized by Barlett & Steele, AHCJ, SABEW, and others. Send story tips to k.fiore@medpagetoday.com. Follow

Disclosures

The work was funded by the Animal Health Diagnostic Center at Cornell University, the Oklahoma Animal Disease Diagnostic Laboratory at Oklahoma State University, and Texas A&M Veterinary Medical Diagnostic Laboratory. It was supported in part by the USDA-National Institute of Food and Agriculture.

The authors reported no financial disclosures.

Primary Source

Nature

Source Reference: Caserta LC, et al "Spillover of highly pathogenic avian influenza H5N1 virus to dairy cattle" Nature 2024; DOI: 10.1038/s41586-024-07849-4.

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Study Raises Questions About Key Features of H5N1 Infection in Cattle - Medpage Today

THURSDAY, July 25, 2024 (HealthDay News) -- The bird flu is now jumping between species of mammals, a step that draws the virus closer to hopping into human beings, a new study warns.

Researchers have tracked transmission of avian influenza between dairy cows in herds, as well as from cows to cats and a raccoon.

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, said senior researcher Dr. Diego Diel, director of the Virology Laboratory at the Animal Health Diagnostic Center in the Cornell University College of Veterinary Medicine.

Still, genetic analysis of the virus did not reveal any mutations that would lead to enhanced transmissibility of H5N1 in humans, Diel said. The findings were published July 25 in the journal Nature.

However, mammal-to-mammal transmission does raise concerns that the virus might eventually adapt to spreading in humans, Diel said.

So far, 11 human cases have been reported in the United States, with the first dating back to April 2022, researchers said.

Four human cases are linked to cattle farms and seven to poultry farms, including an outbreak of six cases over the last few weeks in Colorado, researchers said.

These recent human cases contracted the same bird flu strain identified in the study as the one circulating in dairy cows, researchers said.

Luckily, all human cases to date have had mild symptoms, and the virus has not developed an ability to pass easily between humans.

The concern is that potential mutations could arise that could lead adaptation to mammals, spillover into humans and potential efficient transmission in humans in the future, Diel said in a Cornell news release.

For the study, researchers used genetic sequencing to track the viral strains that transmitted between cows when infected animals from Texas were moved to a farm with healthy cows in Ohio.

They also found that the virus was transmitted to cats, a raccoon and wild birds found dead on affected farms.

The cats and raccoon likely became infected from drinking raw milk from infected cows, researchers said.

More than 100 million cases of avian flu in poultry have been reported in the United States, and 168 dairy herds have been affected, the U.S. Centers for Disease Control and Prevention says.

Outbreaks in poultry have been reported in 48 states, and 13 states have had outbreaks in dairy cows.

More information

The U.S. Centers for Disease Control and Prevention has more about the bird flu.

SOURCE: Cornell University, news release, July 24, 2024

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Bird Flu Is Now Transmitting Mammal-to-Mammal: Study - HealthDay