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How worried should we be about bird flu? Some have warned that avian flu will be the next deadly pandemic. Others have said the risk is no different from what it was a few years ago.

There’s no denying that outbreaks of the virus have had a huge impact on birds in recent months, and that the current outbreak is significantly worse than what we’ve seen in the past. Bird flu has been found in a range of mammals, too, including cats, foxes, otters, seals, and sea lions—and appears to have spread in a mink farm in Spain. We’ve also seen a small number of cases in people.

It is undoubtedly worrying. But there’s no need to panic. Yet.

Deadly bird flu outbreaks are, to some degree at least, our fault. The first were in farmed poultry, and the cramped conditions of housed or caged animals can provide an ideal breeding ground for viruses. “The strains of avian flu that are around today did seem to emerge in poultry,” says Alastair Ward, a wildlife biologist at the University of Leeds in the UK.

What’s less clear is how the virus then spreads back and forth between wild and farmed birds. This seems to happen every year as migrating birds travel along their international flyways, bringing viruses from one region of the world to another and back again.

But last year was different. Instead of seeing seasonal spikes in the virus, we’ve seen prolonged outbreaks, says Ward. The virus seems to have hung around—probably in the environment or in the birds themselves.

This is devastating news on its own. Millions of birds have died. In the US, over 58 million birds have been affected by the virus since the start of last year. Some have tested positive for the virus. Others have been members of an affected flock. The vast majority of these have been commercially farmed poultry, but wild birds have also been badly hit. Take the near-threatened Dalmatian pelican, for example. In 2022, the virus killed off 10% of the global population of these birds.

There’s another concern. The virus appears to have already undergone some kind of mutation that enables it to infect more birds, says Ward. What if a future strain can spread between people?

Spread of the virus between other mammals could be a likely intermediate step between bird-to-bird and human-to-human transmission. Which is why the report of an outbreak in a mink farm in Spain last month rang alarm bells. We’ve also heard reports of bird flu in many other mammalian species, including bears, skunks, raccoons, seals, bobcats, and red foxes in the US, and foxes, otters, and seals in the UK.

There are two ways that viruses can “jump” between species, says Ward. It is likely, for example, that the mammals mentioned in the recent reports picked up the virus from infected bird carcasses. The bodies of a group of birds that had died from bird flu would be “heaving with virus,” as Ward puts it. If a fox tried to make a meal of these birds, it might find its immune system overwhelmed with virus. That could be fatal for the fox, but it wouldn’t necessarily be able to pass the virus on to another fox.

A second type of jump would be more worrying. For now, bird flu rarely affects people. But viruses can mutate rapidly. Different strains can grab genetic sequences from each other, which could help them survive or spread. If a new variant were better able to infect mammals—including humans—it might be able to spread between them. 

That would be a concern, and could well form the beginnings of another pandemic. But we don’t yet have conclusive evidence that this jump has happened.

Even the mink farm outbreak could just have been another example of huge amounts of virus making individuals sick, says Ward. This farm housed almost 52,000 animals in rows of metal cages. Wild birds in the region had recently died with the virus. We don’t know how the virus got into the farm, or how it spread among the animals.

All of those animals were culled. If you’re getting déjà vu, it might be because millions of minks were killed in 2020 after scientists found that a form of the virus that causes covid-19 could spread between them, and to people. You’d hope we’d have learned some kind of lesson between then and now. Sadly not.

Anyway, back to people. None of the people working at the Spanish mink farm seemed to pick up the virus. Only one person developed a runny nose, and he tested negative.

That doesn’t mean people can’t get bird flu. There was a frightening outbreak in Hong Kong in the 1990s, in which hundreds of people died. And last year, a small number of people tested positive for the virus, including a man in England who kept 20 ducks in his home and a person in the US who was involved in culling poultry that were thought to have the virus.

But when it comes to people, at least, not much has changed in the last year. There’s no new convincing evidence that bird flu is more likely to cause a human pandemic now than it was in previous years.

If the last few years have taught us anything, it’s that vigilance is crucial. We do need to closely observe how viruses in animals are developing, and be prepared to tackle a jump to humans. We don’t need to panic, though. Not yet, anyway.

Read more from Tech Review’s archive

We’ve been here before. Scientists were trying to work out how bird flu might make the jump to humans back in the 2000s, as Emily Singer wrote. 

Close monitoring of viruses’ ever-changing genomes has helped us navigate the covid-19 pandemic. It will be vital for future public health threats too, as Linda Nordling wrote last year.

It takes a long time to make a flu vaccine. But the next generation of mRNA vaccines could protect against flu—along with a bunch of other viruses—and could be whipped up in a fraction of the time it takes to make existing vaccines, as I wrote last month.

New mutations that allow viruses to jump from animals to humans can happen anywhere, at any time. But that won’t stop some people from insisting they’ve been concocted by scientists in a lab. Shi Zhengli, who has long studied coronaviruses in bats at the Wuhan Institute of Virology, had to deal with these accusations during the covid-19 pandemic. Jane Qiu covered her story last year.

Tech Review has been covering pandemics since 1956. Apparently back then it was perfectly fine to write that “the people of this world have been molested by a long series of awesome epidemics.”

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