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Comment by parasense | Hacker News Reader

I would imagine that a virus would eventually adapt/evolve to a point to where it co-exists harmoniously with the host organism. I've heard somewhere that herpes simplex virus used to have terrible symptoms, like genital blisters, but over the years the most common variant has no symptoms, and most people have no idea they have it.... and a huge proportion of human have it.

I would imagine all viral contagions would eventually go that route. Because a virus cannot propagate if the host organism goes extinct, or for whatever reason the host organism is itself not fit for survival, or diminished in any way.... anything that might impact virus propagation.

I've read some where the common cold was probably a pandemic virus originally, and it mutated to a common cold we have today, and we mutually evolved to deal with the common cold. Something like that...

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There's no guarantee that it will work that way: smallpox didn't get less deadly. Only vaccination wiped it out.

If the patient is contagious before developing symptoms, the virus can spread very effectively even if many patients die.

> If the patient is contagious before developing symptoms, the virus can spread very effectively even if many patients die.

For better or worse all that means is that viruses may evolve to delay their symptoms rather than overall peak severity if that's possible. It means still just as delay but with a good enough delay to spread.

I don't really see the selective pressure however for this virus to become more benign. It seems to have enough people to infect without it given how contagious it is. It doesn't really have to become more benign to allow even more spread.

The problem with becoming benign is the competition between needing to be breathed out onto people before the immune system destroys it, and respiratory diseases have never not been nasty.

Arguably covid is already less deadly, the majority of deaths are concentrated in older populations. Generally the disease isn't as impactful to those under 50, meaning its not interfering with your ability to have children or raise children.

Age and Date Data: [https://www.cdc.gov/nchs/nvss/vsrr/covid_weekly/index.htm#Se...]

Smallpox also isn't nearly as prone to mutation as covid either.

> I would imagine that a virus would eventually adapt/evolve to a point to where it co-exists harmoniously with the host organism.

Well, how much of our own actual DNA is nothing but virus DNA that got stuck in there for nigh eternity?

Answer: 8%.[0]

[0] https://www.cshl.edu/the-non-human-living-inside-of-you/

DNA integration won't happen with COVID though, it's not a retrovirus so it stays as RNA. I dunno what coexisting looks like for such viruses - maybe like the common cold.

> I've read some where the common cold was probably a pandemic virus originally, and it mutated to a common cold we have today, and we mutually evolved to deal with the common cold. Something like that...

A factor that comes into play is the following. Diseases tend to be less dangerous to children. When a new disease emerges, no-one has immunity to it, so there's plenty of adults who may get it more severely. But, after a certain point, the people being born are exposed to that disease when they are young, where it won't affect them as badly.

This can look like the disease getting milder, but it's just that after a while most people will experience it when young when they will get milder effects from it. And after that point they'll have some immunity for it.

Viral evolution can go down that path, provided there are selection pressures that select for weaker viruses. Viral evolution can also not follow that path at all. Evolution doesn't have a chosen path, and it doesn't have an end-goal. Evolution is the name that we give to the effect that chance has on genetics.

The selection pressure that can select for weaker viral variants is the rapid and widespread deaths of viral hosts. The stronger viral variants literally die off in the hosts they kill, and can't keep spreading, whereas the viral variants that didn't kill their hosts before spreading their genes can keep replicating.

The majority of people with COVID do not die before spreading it to other people. That selection pressure isn't there for COVID, therefore there is nothing really stopping it from mutating into stronger variants. If it starts killing people like Ebola does, then the selection pressure for weaker variants might exist because a lot of hosts will die. Even in that case, it isn't a given that a highly fatal virus would mutate to become weaker. It could very well wipe out entire species and die off itself like the majority of species in the history of the Earth, or it could become endemic in a different species afterwards and live on.

All of this selection happens over evolutionary timelines, which span over many human lifetimes. If the virus becomes weaker, it could take many human lifetimes to reach that point.

From the AP's "Viruses can evolve to be more deadly" article[1]:

> “Becoming more transmissible and less lethal are absolutely what’s best for the pathogen,” said Day. “But the problem is that it’s not always possible, and in many instances is never possible, to be more transmissible and also less lethal.”

> Day said there are documented cases of animal viruses that evolved over time to become more lethal, including myxoma virus in rabbits and Marek’s disease in chicken.

> Some viruses provoke severe symptoms in their hosts that make it easier to transmit the virus to others. But those same symptoms can wind up killing the hosts.

> Adalja said one example is Ebola, a deadly virus that spreads through the blood and body fluids of infected people. Another example is norovirus, which causes diarrhea and vomiting, and leads to hundreds of deaths each year in the U.S.

> “The virus, speaking anthropomorphically, just wants to spread and have its genes replicated,” said Adalja. “If the best way for it is to spread by causing severe symptoms it will continue to do that.”

[1] https://apnews.com/article/fact-checking-011488089270

Yes; and additionally, there's non-sterilizing vaccine immunity at play. If the vaccines are highly effective at keeping people alive, but less effective at teaching the immune system to sterilize it as quickly as possible, that removes some evolutionary pressure which would naturally kill off more lethal mutations. In other words, a more lethal "viral payload" mutation could have its lethality kept in check by vaccines which are good at targeting the spike protein, until a second mutation comes around on that spike protein which better escapes the vaccines; or, simply, until it transmits to a population that is undervaccinated or has waning natural or vaccinated immunity and isn't getting revaccinated.

Given all the other mammal reservoirs that Covid has found, we're just probably the most numerous one and it won't bat an eye (pun intended) if we die off.

> I would imagine all viral contagions would eventually go that route.

There is no intelligence making this decisions, its just some random mutations, so we cannot predict what path the virus will take.

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