This might be a stupid question, but I feel unable to assess that, so I've decided to ask anyway.

My assumptions:

  1. RNA Viruses mutate always, all the time.
  2. Mutations with milder symptoms are likely to spread faster because affected person are less likely to isolate themselves.
  3. Mutations with severe symptoms are likely to spread slower because affected persons are isolating more often and other humans in proximity are more careful. (With the limited exception of mutations that are just reproducing faster)
  4. Mutations that spread faster supplant mutations that spread slower.
  5. Natural human behavior makes a virus mutate towards less severity. Because milder symptoms get rewarded and more severe symptoms get punished.

But now that we are testing anybody for covid19 regardless of the symptoms and put persons with mild symptoms in quarantine for 10 days. Mutations with more severe symptoms might spread faster, especially when affected persons get hospitalized.

Is this chain of though actually a thing? Or is this just more evidence that I'm sitting on top of mount stupid, regarding to covid19?

1 Answer 1



The reason it doesn't is because, assuming the quarantine is effective, the more virulent strains get identified earlier, separated earlier and stopped from spreading by the quarantine. This effectively means that those more virulent viruses are eliminated from the gene-pool. Whereas a less virulent strain is less likely to get noticed, so it can spread further, faster. This is your point 3.

We have seen this with the original SARS-CoV (AKA SARS-CoV-1), which circulated in 2003. With this virus, about 9% of those infected died (c.f. 1-2% with SARS-CoV-2). Because of its high case fatality rate and severity of illness, it was identified early and spread was effectively stopped by... quarantine of those infected.

Quarantine of mild and asymptomatic cases, merely means that those are also removed from infecting others, thereby the overall disease burden on the population is reduced.

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