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This week US officials reported a case of H5N1 influenza in a pig in the Oregon. While it’s certainly a noteworthy finding, as is unfortunately now typical, a lot of the social media buzz is overblown. This is a concerning situation that we need to watch, and yet another indicator that we need to continue to up our game when it comes to H5N1 influenza, but this finding is neither unexpected nor a harbinger of doom.

Here are some of the key points from the report:

  • H5N1 influenza was detected in a pigs and poultry on a small non-commercial backyard farm in Oregon.
  • There were only five pigs on the farm; they were healthy but were tested as part of the response to the infected poultry. Initially only one of the five tested postive.
  • The pigs were euthanized as part of the response (along with the poultry). From some standpoints that makes sense as a precaution against further spread. However, it also means euthanizing animals (that may have even been pets) that possibly could have been effectively isolated and would have recovered from infection (as most pigs do with flu), thereby also missing an opportunity to see what happens in pigs after exposure to better understand risks.
  • More testing was done after the pigs were euthanized. Two pigs tested negative, one was still positive, and results are still pending for the other two.

Here are the concerning bits:

  • We simply don’t want this virus being transmitted to more animals and more species. Every mammal that gets infected with this H5N1 strain creates more potential for the virus to adapt to mammals, potentially creating more risk to people (and other mammalian species).
  • We really don’t want this virus being transmitted to species that have their own influenza A viruses and/or that are susceptible to human influenza viruses. Both of those apply to pigs. If a pig gets infected with H5N1 and another flu virus at the same time, the viruses can get “mixed” within the pig and recombine to make a new flu virus that might be more transmissible to and between humans, but still far enough removed from the current seasonal human flu strains that no one would have any pre-existing immunity from vaccination or previous infection. That’s how new pandemics start.

Here are the good bits:

  • This is one of many, many spillovers of this flu strain into wild and domestic animals (okay, that’s not really good news but it’s important context). In many ways spillover into these pigs is no different than the countless other spillovers into other animals that didn’t get any press (and the world did not end).
  • This was a small backyard farm with only five pigs, so the odds are exceptionally low that there was a separate strain of flu circulating in the pigs on the farm at the same time.
  • The pigs on the farm shared water sources, housing and equipment with the infected poultry, so in some ways I’d be surprised if they didn’t get infected. How pigs are raised, including co-housing with other species and outdoor access, has many trade-offs, especially from a biosecurity standpoint.
  • This was probably a dead end host situation, whereby the pig(s) got infected from the birds, but there was no onward transmission from the pigs to any other animals or people, and therefore plays no role in further viral evolution.

My guess is that, despite all the doomsday prophesies on social media, this specific event will be a nothing-burger. It’s a spillover to a domestic animal that’s probably not anywhere unique as we think, since we probably miss the vast majority of these and they do not go on to contribute to further transmission of the virus. At the same time, it’s a warning shot that so long as this virus continues to circulate, we have a continual risk of it becoming something worse.

I’m not worried about the current H5N1 virus. It’s not a big deal.

I am wary of what the current H5N1 virus could become, under the risk circumstances. The virus keeps getting opportunities to change. Unfortunately we can’t control H5N1 in wild birds, so it’s clearly going to be around for a long time, if not permanently. I believe we can do a much better job of trying to control it in dairy cattle, and we can (and should) also be more proactive and ready to act (actually act, not just talk about acting…) when there are other spillovers into domestic animals.