What to know about the risks of the bird flu outbreak

What to know about the risks of the bird flu outbreak

Avian Influenza Outbreak in U.S.: What We Know So Far

Avian Influenza Outbreak in U.S.: What We Know So Far

The recent spread of avian influenza in dairy cattle in the U.S. has startled even some scientists who've tracked a global outbreak of the virus over the last few years.

"There's a heap of unknowns right now," says Richard Webby, a virologist at St Jude Children's Research Hospital.

How widespread is the virus in dairy cattle? What could this mean for humans? None of this is clear yet.

The first cases of this H5N1 bird flu strain emerged in North America among wild migratory birds in late 2021 and soon spread to poultry farms. It's now showing up among dairy cows and at a major egg producer and one person who had close contact with cows has been infected. This particular version of the H5N1 virus is teaching us that some of the things we thought we knew about flu were wrong," Webby says.

The current outbreak has affected many new wild bird species and persisted for longer than previous ones. The virus has also popped up more often in mammals, both in the wild and on farms, and at times led to a wave of infections and death.

"We are in fairly unprecedented, uncharted territory, globally in relationship to avian influenza," says Dr. Peter Rabinowitz, director of the UW Center for One Health Research. But federal officials and scientists stress the risk to the public still remains low.

So far, the virus does not appear to have mutated in a way that would make it significantly more dangerous. While concerning, the one human case, they say, is consistent with how people usually catch these viruses, through direct exposure to a sick animal.

What Scientists Are Learning:

  1. Genetic sequencing shows 'minor' changes in the virus, nothing alarming
  2. While it's still early days, Webby says the genetic sequencing collected from infected cattle hasn't turned up anything that "immediately screams, this virus has changed, and that's why these cows are getting infected."

    Sequencing of the virus in the Texas patient did show "minor changes," including one mutation associated with viral adaptation to mammals that's appeared in other human cases, according to a report from the Centers for Disease Control and Prevention. However, there's no indication from those previous infections that this mutation makes the virus more likely to spread among humans.

  3. Human-to-human spread of bird flu remains extremely rare
  4. It's generally rare for people to catch any type of bird flu and human-to-human spread is even rarer. During the current outbreak, this version of H5N1 has only been detected in a handful of humans in the last few years globally, and there aren't any documented cases of human-to-human transmission.

  5. Cows may be spreading it to one another, but it's not proving deadly
  6. A central question for scientists right now is whether there's significant transmission of the virus between dairy cattle. Cases have been detected in herds in Texas, Michigan, Kansas, and New Mexico, and are suspected in other states, as well.

  7. Sustained spread between mammals could potentially lead to more problematic mutations
  8. Currently, it's not clear exactly how bird flu is spreading among mammals, and to what extent infections are mostly happening after some kind of contact with infected birds. But scientists worry about sustained mammal to mammal transmission of avian influenza because that gives the virus more opportunities to adapt to that host and acquire mutations that could make it better suited to mammals.

  9. An existing bird flu vaccine could be tapped and adapted in case of human spread
  10. An ongoing outbreak in livestock not only threatens the industry but also makes it more likely that other animals will be exposed, or the workers themselves. "In general, we have not paid a lot of attention to these workers, even though they've often been sort of like the canary in the coal mine, the first evidence of a transmission event," says Rabinowitz. Federal health officials stress that they are taking the situation seriously.

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