Hacker News Reader

Comment by paulmd | Hacker News Reader

Which was projected to be the trajectory from the start. Transmissible diseases usually mutate to be less deadly over time, because killing the host is a bad reproduction strategy. Spanish Flu is still here today, it's just not crazy deadly anymore.

It's just not guaranteed to be monotonic (particular strains can bump lethality upwards), and it doesn't help the people who die early on to the stronger strains, especially with an overloaded medical system.

Like, we don't have hospitals overflowing into makeshift tent farms outside with freezer trucks used to handle the overload of bodies until the crematoriums can get around to them anymore, either. It's definitely trended towards reduced lethality over time.

View on HN

> Transmissible diseases usually mutate to be less deadly over time, because killing the host is a bad reproduction strategy.

Incorrect. This virus has already spread by the time you're dying in the hospital and it doesn't "care" if you die or not. If it could spread more effectively during the transmissible period of the disease, while more effectively murdering you on the tail end, it'll murder you more, no problem.

The Delta wave was a good example of the virus mutating to become both more transmissible and lethal, quite successfully from its perspective.

The mechanism for waning virulence is that we've got T-cells which recognize conserved T-cell epitopes so the human race has some level of relatively permanent immunity now against the novel virus, and because immunity to neutralizing antibodies causes the virus to mutate and it is always competing with the immunity to its past self and that has a cost.

Are you saying AIDS has gotten less deadly over time?

If you take into account the lifecycle of HIV, it can take 2-15 years to develop stage 3. (Stage 3 is the symptomatic part. People on medication may never reach stage 3.) As such, a transmission generation even of SARS-CoV-2 is going to be on the order of days. HIV can be on the order of years.

So, there are different evolutionary pressures. If we find out that Covid is actually latent in all of us years later (unlikely because we would have likely seen it with SARS-1 or MERS), then all bets would be off.

This makes sense. Would also make sense why AIDS hasn't evolved to become less deadly, but it also brings up that covid hasn't had a bottleneck in terms of transmission. The main reason why one strain has replaced another has been that more recent strains are more transmissible. Delta was more deadly (and transmissible) than alpha, beta & the original strain, and came later for instance. I think we got lucky with omicron, which evolved from alpha if i'm not mistaken.

Yes. The latest variants are less deadly. There is a pretty good reason for that. If the infected lives longer it has a higher chance of a successful transmission.

What are you basing this on? Looks like deaths peaked in 2004, but more people in Africa are receiving treatment. Without treatment the avg life expectancy seems to be 11 years, and doesn't look like that's changed.

I think there are several factors in when the deaths peaked.

https://www.bbc.com/news/health-30254697

Can you link to a source?

https://www.bbc.com/news/health-30254697

I think it actually has - AIDS is the worst but life expectancy has improved a lot

Because of better treatments? or has it really just been the AIDS virus evolving?

I imagine we won't know because of HIV's long life in the body, properly medicated. No one is willing to run a study to determine that, as it essentially sentences the control group to death.

Reply on news.ycombinator.com