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In early March, Dr. Barb Peterson, a large-scale veterinarian in Texas, began receiving calls from dairy farms operating in the Panhandle. Workers there were seeing many cows with mastitis, an infection of the udder.

Their milk was thick and discolored and could not be explained by the usual suspects, such as bacteria or tissue damage.

Many more dairy products are called. One landowner told her he thought his farm “had something going around, and half my livestock was dead,” suggesting the disease had gone beyond cattle.

After running a battery of tests and ruling out any possible cause, Peterson sent samples from sick and dead animals to friends and colleagues at Texas A&M State Veterinary Laboratory and Iowa State University.

What they found – many HIV He also created a list of urgent scientific tasks. One of the questions that needs to be answered is how the virus was infecting cows in the first place.

Researchers in America and Denmark have taken this task. Their findings, as published Pre-print Research shows cows have the same receptors for flu viruses as humans and birds. Scientists fear that cows may mix bowls – hosts that help the virus learn to spread better between people. Such an event, while rare, experts say, could put us on the path to another epidemic.

For years, H5N1, or highly pathogenic avian influenza, was primarily confined to bird populations, but recently it has begun infecting a growing number of mammals, suggesting the virus may be adapting and moving closer to becoming a human pathogen.

Avian influenza viruses have decimated commercial poultry flocks in the U.S., and because pigs are known to carry bird flu viruses, pigs are closely monitored for signs of infection — but cows were not on anyone’s radar as potential hosts.

The U.S. Department of Agriculture says 42 infected herds have been found in nine states since late March. Only one person was infected with H. In cooperation with the states to control people who have exposure to animals.

Dr. Lars Larsen, a professor of veterinary clinical microbiology at the University of Copenhagen in Denmark, said: “The findings in cattle are very different.” In mammals, influenza typically attacks the lungs. In cats, it can also infect the brain. “We see very high levels of virus in the breast and in the milk,” Larson said.

Larson said the amount of H5N1 viruses in the milk of infected cows was 1,000 times higher than that of normally infected birds. He and his colleagues calculated that even if it were dissolved in 1,000 tons of milk from one cow’s milk, scientists could detect traces of the virus in a laboratory test.

A U.S. Food and Drug Administration investigation found genetic material from the H5N1 virus in about 1 in 5 samples of milk purchased on grocery shelves, raising questions about how the virus spread. Researchers later confirmed that the pasteurized milk tested was not contagious and could not make anyone sick.

That outbreak hasn’t stopped him from shaking more than a few nerves. There is big money riding on the health of cows. In 2022, milk and dairy products were the fourth largest agricultural products in the US in terms of cash receipts; according to USDA Economic Research Service. The sale of cattle and calves was the second largest product.

Viruses need a way to invade cells. The key to the virus that causes Covid-19 is a receptor called ACE2. For flu viruses, it’s a sugar molecule that sticks to the surface of cells called silicic acid.

Different animals contain different forms or forms of sialic acids. Birds have sialic acid receptors that are slightly different from those in the upper respiratory tract of humans.

If you hold your index finger straight up, this is what a bird’s silicic acid receptor looks like, says Dr. Andy Pekosz, a molecular microbiologist and immunologist at Johns Hopkins University. If you bend your finger down at the knee to an L, this is what the human sialic acid receptor looks like. Influenza viruses prefer to bind to one form over another, he said.

Researchers think this is one reason why H5N1, from birds, has not been seen to spread efficiently between humans.

Until recently, no one knew what kind of sialic acid receptors cows had, because it was believed that they did not carry A-strain flu viruses such as H5N1.

Larsen and his colleagues took tissue samples from the lungs, windpipes, brains and mammary glands of calves and cows in the US and Denmark and stained them with compounds known to bind to various sialic acid receptors. They cut the infected tissues very thinly and looked at them under a microscope.

What they saw was surprising: the alveoli, the tiny milk-producing sacs in the breast, were filled with sialic acid receptors, and they had receptors both common to birds and common to humans. Lead study author Dr. Charlotte Christensen, a postdoctoral researcher in veterinary medicine at the University of Copenhagen, said almost every cell they looked at contained both types of receptors.

That finding is troubling: One way flu viruses mutate and grow is by swapping genetic material with other influenza viruses. This process, called recombination, requires a cell to be infected by two different flu viruses at the same time.

“If you get both viruses in the same cell at the same time, you can get hybrid viruses,” said Dr Richard Webby, director of the WHO Collaborating Centre. In animals and birds.

To be infected by two flu viruses at the same time – the bird flu virus and the human flu virus – a cell must have both types of sialic acid receptors, which cows do, something that was unknown before this study.

For 25 years, H.

For this to happen, a cow infected with the bird flu virus would have to get a different type of flu than an infected person. Currently, human flu infections are low across the country and will decrease as the flu season winds down, making the likelihood of something like this even more remote.

Still, it’s not unheard of.

Pigs have both human and avian silicic acid receptors in their respiratory tract, and influenza infection in pigs is known to stimulate pandemic viruses. For example, the 2009 pandemic caused by H1N1 influenza is believed to have started In pigs in Mexico When the virus is reassigned to one that can spread quickly between people.

Another way the bird flu virus can mutate in cows, Webby says, is slowly — and more commonly.

Every time a virus copies itself, it makes a mistake. Sometimes, those mistakes make the virus less viable and hurt its chances of survival, but in other cases, they’re happy accidents — at least for the virus. If the bird flu virus could be modified to bind more easily to human-type sialic acid receptors in cows, it could gain a survival advantage: the ability to infect more cells and more animal types, such as humans.

Viruses can slip and slide

Reassortment is a major change in virus evolution, but gradual transmission of the virus through new hosts can also cause changes in the evolving virus genome.

Dr. Sam Scarpino, director of AI and life sciences at Northeastern University, is a computational biologist and AI scientist.

“We now have data that indicates the risk profile is higher,” said Scarpino, who was not involved in the new study.

Note that this is a preliminary study. It must be verified by a separate team of researchers and quickly published as a preprint before being reviewed by outside experts.

But the findings are also important, he said, because no one has ever really looked at the susceptibility of cow tissue to the influenza A virus.

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“This is the first I know. Not that there aren’t others out there, but many of us have looked carefully and found none.

According to Christson, the researchers could not find any previous research, which is why they did the study.

“Given the circumstances, we felt we had to go with these results as quickly as possible,” Larson said.

Other experts say that although there are many points to connect, the study clearly raises the level of consciousness.

“I think we have more than enough information to conclude what should happen now, we have to stop the transmission in dairy cattle,” said Scarpino. “We need to increase the protections mandated for workers who come into close contact with cattle and dairy products and significantly increase funding for understanding influenza and cows, because there is a huge amount we don’t know. We need to learn quickly.”