Bird flu is bad for poultry and dairy cows. It’s not a dire threat to most of us – yet.

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Headlines are flying after the Department of Agriculture confirmed that the H5N1 bird flu virus has infected dairy cows across the country. Testing has detected the virus among cattle in nine states, mainly in Texas and New Mexico, and most recently in Colorado, Nirav Shah, principal deputy director of the Centers for Disease Control and Prevention, said at an event. May 1st event carried out by the Council on Foreign Relations.

A menagerie of other animals was infected with H5N1 and at least one person in Texas. But what scientists fear most is that the virus will spread efficiently from person to person. This has not happened and may not happen. Shah said the CDC considers the H5N1 outbreak “a low risk to the general public at this time.”

Viruses evolve and outbreaks can change quickly. “As with any major outbreak, this one is moving at the speed of a bullet train,” Shah said. “We will be talking about a snapshot of that speeding train.” What he means is that what is known today about H5N1 bird flu will undoubtedly change.

With that in mind, KFF Health News explains what you need to know now.

Q: Who gets bird flu?

Mainly birds. In recent years, however, the H5N1 bird flu virus has jumped more and more from birds to mammals across the world. The growing list of more than 50 species includes seals, goats, possums, cats and wild dogs at a UK zoo. At least 24,000 sea lions died in outbreaks of H5N1 bird flu in South America last year.

What makes the current cattle outbreak unusual is that it is spreading quickly from cow to cow, while other cases – except for sea lion infections – appear limited. Researchers know it because the genetic sequences of the H5N1 viruses extracted from cattle this year were almost identical to each other.

The cattle outbreak is also worrying because the country was caught off guard. Researchers examining virus genomes suggest it originally spread from birds to cows late last year in Texas, and has since spread among many more cows than have been tested. “Our analyzes show that this has been circulating in cows for about four months, right under our noses,” said Michael Worobey, an evolutionary biologist at the University of Arizona in Tucson.

Q: Is this the start of the next pandemic?

Not yet. But it’s an idea worth considering because a bird flu pandemic would be a nightmare. More than half of the people infected with older strains of the H5N1 bird flu virus from 2003 to 2016 died. Even if mortality rates turn out to be less severe for the H5N1 strain currently circulating in livestock, the repercussions could involve too many sick people and hospitals too overwhelmed to deal with other medical emergencies.

Although at least one person has been infected with H5N1 this year, the virus cannot lead to a pandemic in its current state. To achieve this horrible status, a pathogen needs to sicken many people on several continents. And to do that, the H5N1 virus would need to infect a ton of people. This will not happen through occasional spillovers of the virus from farm animals to people. Instead, the virus must acquire mutations to spread from person to person, like the seasonal flu, as a respiratory infection transmitted largely through the air when people cough, sneeze and breathe. As we learned in the depths of Covid-19, airborne viruses are difficult to stop.

That hasn’t happened yet. However, H5N1 viruses now have many chances to evolve as they replicate in thousands of cows. Like all viruses, they mutate as they replicate, and mutations that improve the virus’s survival are passed on to the next generation. And because cows are mammals, viruses may be growing better in cells closer to ours than in those of birds.

The evolution of a pandemic-ready bird flu virus could be aided by a kind of superpower possessed by many viruses. In other words, they sometimes exchange their genes with other strains in a process called rearrangement. In a study published in 2009, Worobey et al. researchers traced the origin from the H1N1 “swine flu” pandemic to events in which different viruses causing swine flu, bird flu and human flu mixed and matched their genes in pigs that they infected simultaneously. Pigs don’t need to be involved this time, Worobey warned.

Q: Will a pandemic start if a person drinks milk contaminated with viruses?

Not yet. Cow’s milk, as well as powdered milk and infant formula sold in stores, are considered safe because the law requires that all milk sold commercially be pasteurized. This process of heating milk to high temperatures kills bacteria, viruses and other small organisms. The tests identified fragments of the H5N1 virus in supermarket milk, but confirmed that the pieces of the virus are dead and therefore harmless.

However, unpasteurized “raw” milk has been shown to contain live H5N1 viruses, which is why the FDA and other health authorities strongly advise people not to drink it. Doing so can make a person seriously ill or worse. But even so, a pandemic is unlikely to be triggered because the virus – in its current form – does not spread efficiently from person to person, as seasonal flu does.

Q: What should be done?

Quite! Due to a lack of vigilance, the U.S. Department of Agriculture and other agencies allowed H5N1 bird flu to spread unnoticed in livestock. To control the situation, the The USDA recently ordered All lactating dairy cattle will be tested before farmers move them to other states, and test results will be reported.

But just as restricting Covid testing to international travelers in early 2020 allowed the coronavirus to spread undetected, testing only cows that cross state borders would miss many cases.

These limited tests will not reveal how the virus is spreading among livestock – information desperately needed so farmers can stop it. One main hypothesis is that viruses are being transferred from one cow to another through the machines used to milk them.

To boost testing, Fred Gingrich, executive director of a nonprofit organization for agricultural veterinarians, the American Association of Cattle Practitioners, said the government should offer funding to livestock farmers who report cases so they have an incentive to get tested. . Barring that, he said, the reports only add reputational damage to financial losses.

“These outbreaks have a significant economic impact,” Gingrich said. “Farmers lose around 20% of their milk production in an outbreak because the animals stop eating, produce less milk and some of that milk is abnormal and cannot be sold.”

The government has made H5N1 testing free for farmers, Gingrich added, but has not budgeted money for veterinarians who must collect samples from cows, transport samples and fill out paperwork. “Testing is the least expensive part,” he said.

If on-farm testing remains elusive, evolutionary virologists can still learn a lot by analyzing genomic sequences of H5N1 viruses sampled from cattle. The differences between the sequences tell a story about where and when the current outbreak began, the path it takes, and whether the viruses are acquiring mutations that pose a threat to people. However, this vital research has been hampered by the USDA’s slow and incomplete publication of genetic data, Worobey said.

The government should also help poultry farmers prevent H5N1 outbreaks, since they kill many birds and pose a constant threat of spread, said Maurice Pitesky, an avian disease expert at the University of California-Davis.

Waterfowl such as ducks and geese are the usual sources of outbreaks on poultry farms, and researchers can detect their proximity using remote sensing and other technologies. By focusing on areas of potential impact, farmers can focus their attention. This could mean routine surveillance to detect early signs of infections in birds, using water cannons to scare away migrating flocks, relocating farm animals or temporarily herding them into barns. “We should be spending on prevention,” Pitesky said.

Q: OK, it’s not a pandemic, but what could happen to people who get this year’s H5N1 bird flu?

Nobody really knows. Only one person in Texas has been diagnosed with the disease this year, in April. This person worked closely with dairy cows and had a mild case of eye infection. The CDC discovered them due to its surveillance process. Clinics must alert state health departments when they diagnose flu in farmworkers, using tests that broadly detect flu viruses. State health departments then confirm the test and, if positive, send the person’s sample to a CDC laboratory, where it is specifically checked for the presence of the H5N1 virus. “So far we have received 23,” Shah said. “All but one of them were negative.”

State health department officials are also monitoring about 150 people, he said, who spent time near the cattle. They are talking to these farmworkers through phone calls, texts or in-person visits to see if they develop symptoms. And if that happens, they will be tested.

Another way to evaluate rural workers would be to check whether there are antibodies in their blood against the H5N1 bird flu virus; a positive result would indicate that they may have been unknowingly infected. But Shah said health authorities are not yet doing this work.

“The fact that it’s been four months and we haven’t done this is not a good sign,” Worobey said. “I’m not too worried about a pandemic right now, but we should start acting like we don’t want it to happen.”

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