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RyanW1019 t1_jdj280w wrote

Reply to comment by underbrownmaleroad in What happened to the old COVID variants, like Delta? Could they come back? by number1dork

Whenever a virus replicates, there is a chance for the new virus particles to develop mutations. If these mutations make them less contagious, they will quickly get outcompeted by the old lineage and die out. If the mutations make them more contagious, they will outcompete the other strains until they become the new dominant version that new mutations develop from.

The only upside is that viruses don't usually benefit from becoming more deadly; if anything, that makes them less able to multiply if they kill their hosts. (Exception: if the host becomes very contagious before dying to the virus, more lethal strains could still develop as long as they are able to successfully leap from person to person before their victims die.) So in the long run, many viruses tend to get more infectious but less lethal, since the mechanism that makes a virus lethal is usually complicated and most random changes to it from mutations tend to reduce severity, not increase it.

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underbrownmaleroad t1_jdj3fal wrote

Very cool write up, especially learning how viruses tend to become less lethal and more contagious. It’s like the use us humans as the method for their life and once they reach their max potential it’s like oops yeah I didn’t mean to kill every one on the way

Is there any evidence that colds use to be more deadly and now they’ve reached a point that they’re largely contagious and less deadly?

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Matrix17 t1_jdj64rx wrote

> viruses tend to become less lethal and more contagious

This is not always true. Remember, there has to be some sort of evolutionary selection for it. As an example, the reason delta even became a thing, which was more deadly than the original strain, is because covid was spreading before people had symptoms. So it didn't matter if it killed the host or not, because they likely spread it before they even knew they had it. So there was no selective pressure for it to become less deadly. If covid had only spread after someone was symptomatic, it may not have turned into a pandemic at all

We just got lucky that the omicron mutation happened. If delta was still circulating, we would be in a very bad spot

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Tephnos t1_jdk6rpz wrote

> Very cool write up, especially learning how viruses tend to become less lethal and more contagious.

They don't. It's a myth that continues to be propagated because it sounds logical to the layman. It is our immunity that makes them less lethal (when we survive).

If viruses behaved this way as a given, we wouldn't have been getting killed by smallpox and many other viruses for millennia.

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