Thread by @Donaithnen

I spent some time a week or two ago looking into reports about #H5N1. Since it's back in the news again i figured i would share some of what i learned. I am not an expert! This is just some things that people who seemed well educated on the subject have said. 🧵/20

At this point H5N1 is probably endemic in bird populations around the world. There were some previous waves that were contained by mass culling of domestic birds, but the genie is most likely out of the bottle for good this time.

The rise in egg prices over the last year is only _partly_ due to H5N1 (along with some inflation and some price-gouging.) But one way or another it seems likely to permanently impact egg farming going forward.

Even more mass cullings. Or mass vaccinations. Or a total shift in how chickens are farmed.

In any event, it seems unlikely egg prices will ever go all the way back down to what they were before.

H5N1 also seems likely to have a big impact on ecological balances pretty much everywhere, though what impact exactly is hard to say until we see which species recover and which don't, and how the rest of the ecosystem adapts to that.

On the non-bird front, a large number of mammals have been infected with H5N1, but _most_ of them seem to be isolated cases. However there are a _few_ instances where mammal to mammal spread seems to have been likely.

One of the most concerning was at a mink farm, which is especially worrying because minks and ferrets reportedly have similar respiratory systems to humans and seem to be a likely breeding ground for a variant that can infect humans.

That group of mink (about 50,000) was culled before any human crossover infections could occur. However if we didn't already have enough ethical reasons to ban mink farms this seems like a very good practical reason to do so!

H5N1 is reported as having about 50% fatality in previous cases where humans have caught it. It's _possible_ that the figures were skewed because some people have caught it but didn't report it, or didn't even know they had it, because they didn't feel especially sick.

But there have been about 870 documented H5N1 cases in the last 25 years with 457 deaths, so there would have to have been about 40-50k stealth cases just to get the fatality rate down to about what Covid was initially reported at, which seems very unlikely.

And note that 870 known H5N1 cases over 25 years means an average of 34 cases a year. Though it's definitely a tragedy for the people involved, one or two identified human cases in Cambodia is not necessarily a sign of the apocalypse. It's not even a statistical outlier yet.

On the other hand, reportedly part of the reason H5N1 is so deadly in humans is that it infects our lower respiratory tract, however that is _also_ part of why human to human transmission doesn't happen when a human does get infected.

In the event that we do start seeing human to human transmission it seems quite possible that will be because that variant of H5N1 will have started infecting the upper respiratory tract instead, which in theory should make it less deadly.

Which isn't to say that there's nothing to be concerned about, but even if H5N1 does breakthrough and become a human pandemic that doesn't necessarily mean an apocalyptic "half of everyone in the world dies" scenario like a lot of people keep implying.

Also, there _is_ already an H5N1 vaccine, or at least a vaccine for some variants. However there is currently no plan to start mass producing it until and unless it starts infecting humans on a widespread scale.

So again, i am not an expert on either epidemiology or policy. However it seems to me that H5N1 is certainly something to be concerned about and continue monitoring, but there's no reason currently to panic.

There have been a couple estimates that the odds of there being an H5N1 pandemic "soon" is in the single digits, as long as there are less than 100 cases of human to human transmission in the next six months.

Which is a bit of a truism, but it does mean that until there are 100 such cases there is no reason to panic. If there are 100 or more human H5N1 cases, well, don't _panic_, but proceed with deliberate haste to take precautions?

Personally i feel the US government should already be preparing for mass production of the H5N1 vaccine. And all nations should cooperate to outlaw mink farming as one of the highest risk factors for respiratory viruses crossing over into humans.

And just in case, it would make sense for everyone to keep a supply of N95 or equivalent masks on hand as a precaution, even if you've decided to stop masking for Covid. _If_ an H5N1 pandemic happens you don't want to be caught flat-footed if there's another mask shortage.