[falcolas]

Globalization is a fairly new thing (on the 3.5B year timescale at least), allowing for the spread of any disease quickly. Whereas isolation and evolution has saved us in the past, it might not have the necessary time in the future (imagine if Covid had been even more deadly, for example).

[masklinn]

Prions don't really spread on their own though, yes they are extremely hardy and can survive in soils but that doesn't do anything, if it did and isolation was the only solution we'd have thousands of prion-infested red zones where humans couldn't set foot.

> imagine if Covid had been even more deadly, for example

It'd have been taken more seriously, and it would have had a higher chance of burning itself out. Covid's such a pain in the ass because it hits such a sweet spot, of spreading fast, being highly infectious, and being benign enough (with many of the infected spreading it asymptomatically). For the hell that it is, the one "saving grace" of Ebola is that it debilitates and kills fast enough it's very hard for it to spread, especially as it doesn't have great transmission vectors.

[im3w1l]

What I remember from middle school biology is that nutrients flow in a cycle. Organic matter in the soil will be composted and consumed by earth worms, funghi and microorganisms.

And to them, prions are just organic matter like any other.

[ravi-delia]

In addition to the points other people made, proteins are really a whole different thing from viruses in terms of numbers. You make so many proteins every moment, at this point every possible screwup has been cooked up somewhere.

[andy_ppp]

If COVID were more deadly like Ebola it tends to not have long gestation periods where it can be spread without symptoms.

[est31]

tends to is not going to cut it in this instance. If 99% of diseases are either easy to spread, or deadly, we still need to worry about the 1% that are both. It only takes one such disease to cause a wipeout like event.

[andy_ppp]

I was going to add a flow up edit to add more clarity to my answer; the point is if 50% of people are dying from an airborne disease, getting to zero is going to be treated with much more importance than COVID with a ~2% (? maybe) fatality rate. People who think masks are a political tool to control us suddenly are less paranoid about that (and vaccines, and social distancing) when the bodies are bing piled up in the streets.

I think we'd probably handle a more severe disease with much less flippancy than we did COVID and we'd have to treat lockdown and other tools with much more reverence in such a situation.

This does happen with Ebola outbreaks being managed in Africa now so if they can do it there I think we can do it here.

[stickfigure]

0.7%, not 2% (according to the US CDC). Which does make it "worse" for the reasons you point out.

[est31]

> getting to zero is going to be treated with much more importance than COVID with a ~2% (? maybe) fatality rate. People who think masks are a political tool to control us suddenly are less paranoid about that (and vaccines, and social distancing) when the bodies are bing piled up in the streets.

I agree with the first sentence, but not with the second. Yes, governments might eventually put more care onto reducing covid counts. But a) it might be too late. Just check how long it took for travel restrictions to be imposed.

And b) the panic that people will be in will be even bigger, especially those who think that masks and vaccines are a way to spread microchips and 5G. These folks aren't rational.

Last, there is a non zero chance you'll be dying in the next few years. At that point, do you really care about rules? The governments will impose even stricter lockdown measures. But this will cause even more unrest as people are confined to their homes.

Ebola is in the category of "deadly but not easy to spread". Yes, it can be spread but by the time you spread it you physically can't leave your bed. That's a great help in preventing spread. I'm talking about a disease that at the start has few symptoms, allowing for easy spread, then gets severe and deadly further down in disease progression.

[jMyles]

If COVID19 had been significantly deadly, presumably it would have burned out at the pace of SARS1.

It seems to be close to the sweet spot in terms of being able to spread but still occasionally kill.

[beiller]

If it was more deadly it would spread less quickly. That's how diseases work from my vague university memories of an epidemiology course. They are on a spectrum of deadly to contagious.

[derekp7]

What actually causes this though? For example, take something like HIV that takes a long time to show symptoms, but have an airborne version of it. Do the things that make viruses airborne also keep them from having a long gestation period and also highly lethal?

[akiselev]

> Do the things that make viruses airborne also keep them from having a long gestation period and also highly lethal?

Surviving airborne before the advent of buildings meant surviving outside in direct sunlight with little in the way of protection from droplets or anything else. Organisms have a limited amount of abstract "evolutionary capital" and the costs, so to speak, of developing adaptations to survive airborne and evade an active immune system are astronomical. It's not impossible, but the two "features" work against each other during the development phase.

[danaris]

(Not an immunologist/virologist/biologist of any stripe. The following is my rough layman's understanding of the answer to this question. Would love to be corrected by someone with more formal knowledge of the subject.)

My understanding is that the main reason is a biological application of the principle of parsimony: Evolutionarily, organisms don't generally evolve lots of different things all at once. Thus, if you have a novel variant of a virus, it is highly likely to be mostly like existing variants, but with a very small number of changes.

Basically, you can think of it as the virus having to hit a particular threshold of a mutation direction that increases transmissibility to become widely-spread, but also has to hit a particular threshold of a mutation direction that increases lethality in order to become very dangerous.

As soon as it hits that transmissibility threshold, that is the version of the virus that's going to spread, and hitting both those thresholds at the same time is going to be incredibly rare.

What's much more likely (and genuinely concerning) is the possibility that a virus that has already become highly transmissible evolves more in the "lethality" direction and goes from being a widespread nuisance to being a deadly pandemic. The longer we let something like COVID remain widespread, as I understand it, the more likely we are to see a variant emerge that retains its high transmissibility but also gains a higher lethality. However, as we can see from the fact that the bodies are not piling up in the streets, even after nearly a year and a half of a pandemic form of a particular virus, it's by no means guaranteed that something like that will happen, even at a small scale.

[ASalazarMX]

This is such an interesting question, I hope it doesn't get buried before someone knowledgeable answers it.

We all know the more aggressive a pathogen is, the more it paints itself into a corner because it's burning its bridges. Something like airborne HIV would be really scary.

My guess is that airborne diseases are not weaker, but that evolution has selected for resistance against those because they spread fast among the population.

[lazide]

This is unfortunately just not correct in real life. It’s a good representation of general behavior/trends, but for instance Smallpox was around since at least 500 BC, and still had a 35% fatality rate until it was eradicated in the 70s.

The more times you roll the dice, the more often you’ll get that magic combo of lethal and highly transmissible. For the most part it doesn’t favor it, but that just makes it an outlier when it does, not impossible.

[Sebb767]

At least a part of it is probably the human factor. The big "PR" problem we have with fighting the epidemic is that a lot of people won't have much (visible) problems. If COVID would lead to a slow and painful death 99% of the time, there were probably far fewer people trying to get it or using the herd immunity strategy.

[beiller]

I don't think we know what causes it. It is mainly just observed. What causes this is a very active area of study. Probably some output of a "evolutionary" process of how viruii mutate but my knowledge is very little :)

[vanderZwan]

Sure, but this does not in any way favor prions over other options.