I sent this out to a family chat today, seems useful to post publicly. Original source: Scott Alexander, linked below.
Interesting new information I've learned about the H5N1 bird flu that has been simmering for a few years (I remember when we went to Newfoundland a few years ago, there were signs out for people to please stay away from the duck pond because some ducks were getting H5N1 flus). Full blog post from someone whose writing I read often, who is good at summarizing the current state of scientific knowledge on a given topic (often writes "<topic>: Much more than you wanted to know" posts). https://www.astralcodexten.com/p/h5n1-much-more-than-you-wanted-to
Key takeaways:
- You'll probably see H5N1 news this year, similar to how you've seen it in the past few years. I'm writing this to give you a quick sense of how much to worry.
- The chance of a sustained flu pandemic in humans next year, based on the information we currently have available as of Jan 1 2025, is around 5%. Which is not that much higher than the base rate, since flu pandemics happen every 20 years ish. It's been 16 since the last big one, but sometimes we can go up to 40 years without a flu pandemic.
- If we had a H5N1 flu pandemic in 2025, there's about a 30% chance it would be like "a lot of people get regular flu around the same time", a roughly 60-65% chance it's worse than usual in terms of how sick it makes people, but not like the 1918 flu (say, comparable to the Asian flu of 1957-1958, which had a case fatality rate of 0.2%, compared to COVID's case fatality rate of around 1.3%), 5% chance of being like the 1918 epidemic, and 1% chance of being worse than that. That's a lot of numbers, the take-away is "the chance of a pandemic is low, and if one did occur it probably wouldn't be very bad, Myron will post on this blog (and if you're a friend of his sending you a link to this post, he'll tell you directly) if new information changes this outlook but for now don't worry."
- We have and can make flu vaccines at scale, unlike with COVID at first. If it looks like H5N1 has become particularly deadly to unvaccinated humans, you know what to do.
- But right now H5N1 is quite deadly among chickens, and becoming pandemic and possibly high-fatality among cows. This is likely to increase meat prices, and generate scary news stories in 2025.
Other background:
Approx. all flus start out as bird flus. This one being a bird flu doesn't make it special. Also, the H5N1 designation isn't anything particularly meaningful. Basically, there are two types of molecules that stick off flu viruses, each gets a big word, one of the words starts with H, and another starts with N. There are 18 different H complexes, and 11 different N complexes, meaning you could have like H18N11, or H18 N10, or H1N1, etc. This means something to virologists, but isn't particularly significant to non-virologists.
