7 ms·

Wasn't there news about how as a virus mutates over time it becomes less severe, but more transmissible? Something about where the virus just wants its host to

Wasn't there news about how as a virus mutates over time it becomes less severe, but more transmissible? Something about where the virus just wants its host to live long enough to transmit the virus to someone else so it can continue passing its genetic data over. It seems like Omicron could be following this pattern. If you have too severe of a virus, then all its hosts are killed and it can't live on. Too weak of a virus and the host's immune systems will kill it before it has a chance to transmit.

senectus1 5y ago
>If you have too severe of a virus, then all its hosts are killed and it can't live on. Ever played "Plague Inc" ? Its a fascicle way to show how this model is unlikely to play itself out in todays hyper mobile population.
gonehome 5y ago
With delta and asymptomatic transmission this wasn’t totally the case iirc. Increased viral load in the asymptomatic phase increased virality, but also increased deadliness once the symptoms started. At least that’s what I recall reading. Normally you’re correct, but it doesn’t necessarily need to be that way. Hopefully we’re lucky and it’s both way more transmissible and way less deadly, but no one knows yet.
- tunesmith 5y ago
  Delta was more severe than the original strain, but there was some evidence indicating it was slightly less severe than Alpha (and much more transmissible than Alpha).
irjustin 5y ago
This is true (and hopefully so w/ Omicron) when looked at a long enough time scale. The real concern is if we're currently in the "still getting worse before it gets better" part of the timeline. We're all waiting to see how many severe hospitalizations occur w/ a large enough population.
UncleOxidant 5y ago
> Wasn't there news about how as a virus mutates over time it becomes less severe, but more transmissible? That's sort of a rule-of-thumb, not a fixed law. In the case of covid there's a relatively long period of time (up to several days) in which people can spread the virus without yet showing symptoms. As such there isn't a lot of evolutionary pressure for it to become less virulent.
- simo7 5y ago
  True, there's no selective pressure for it to become less lethal. But I wonder: isn't a random mutation unlikely to improve on any of its profiles (transmissibility or lethality)? If so a more transmissible virus is unlikely to also be more lethal. What if (not sure) a random mutation actually tends to do slightly worse? Then more transmissible viruses tend to be less lethal over time. Sure we still get more lethal mutations from time to time, but the more transmissible ones are the ones which win out.
  - mro_name 5y ago
    > random mutation unlikely to improve indeed, but subsequent success or failure does. Mutation and selection. Mutation prepares the pool to sieve the successful ones.
    - simo7 5y ago
      Yes my point is, when you do improve one (transimissibility) you probably did not improve the other one (or even got worse at it).
  - IneffablePigeon 5y ago
    I'm no expert but my understanding is that unfortunately there is some correlation between transmissibility and severity of disease, because one of the ways it can become more transmissible is to reproduce in your cells faster so that you shed more virus particles. This also means it takes over quicker and your immune system has less time to respond before it does lots of damage. Whether that outweighs the randomness you describe I don't know. Maybe nobody knows for this virus?
foobiekr 5y ago
In order for this to occur, there needs to be a selection pressure. It doesn't just magically happen. The virus behind Marek's disease in chickens hasn't gotten less severe over time, it's gotten much, much more severe, as an example. HIV does not seem to have gotten less severe, nor smallpox.
- mariodiana 5y ago
  The virus behind Marek's disease in chickens got much more severe because of the leaky vaccine used on chickens. Here's some introductory material: https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous https://www.nationalgeographic.com/science/article/leaky-vaccines-enhance-spread-of-deadlier-chicken-viruses https://www.youtube.com/watch?v=haRMKsI-jKY And here are a couple of papers: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002198 https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002236
  - foobiekr 5y ago
    Yes, Marek's is actually a good illustration of how diseases can go in the other direction.
ikr678 5y ago
That's the theory behind spanish flu mutating into the less severe seasonal flu strains we learned to live with.

senectus1 5y ago

>If you have too severe of a virus, then all its hosts are killed and it can't live on. Ever played "Plague Inc" ? Its a fascicle way to show how this model is unlikely to play itself out in todays hyper mobile population.

gonehome 5y ago

With delta and asymptomatic transmission this wasn’t totally the case iirc. Increased viral load in the asymptomatic phase increased virality, but also increased deadliness once the symptoms started. At least that’s what I recall reading. Normally you’re correct, but it doesn’t necessarily need to be that way. Hopefully we’re lucky and it’s both way more transmissible and way less deadly, but no one knows yet.

tunesmith 5y ago
Delta was more severe than the original strain, but there was some evidence indicating it was slightly less severe than Alpha (and much more transmissible than Alpha).

irjustin 5y ago

This is true (and hopefully so w/ Omicron) when looked at a long enough time scale. The real concern is if we're currently in the "still getting worse before it gets better" part of the timeline. We're all waiting to see how many severe hospitalizations occur w/ a large enough population.

UncleOxidant 5y ago

> Wasn't there news about how as a virus mutates over time it becomes less severe, but more transmissible? That's sort of a rule-of-thumb, not a fixed law. In the case of covid there's a relatively long period of time (up to several days) in which people can spread the virus without yet showing symptoms. As such there isn't a lot of evolutionary pressure for it to become less virulent.

simo7 5y ago
True, there's no selective pressure for it to become less lethal. But I wonder: isn't a random mutation unlikely to improve on any of its profiles (transmissibility or lethality)? If so a more transmissible virus is unlikely to also be more lethal. What if (not sure) a random mutation actually tends to do slightly worse? Then more transmissible viruses tend to be less lethal over time. Sure we still get more lethal mutations from time to time, but the more transmissible ones are the ones which win out.
- mro_name 5y ago
  > random mutation unlikely to improve indeed, but subsequent success or failure does. Mutation and selection. Mutation prepares the pool to sieve the successful ones.
  - simo7 5y ago
    Yes my point is, when you do improve one (transimissibility) you probably did not improve the other one (or even got worse at it).
- IneffablePigeon 5y ago
  I'm no expert but my understanding is that unfortunately there is some correlation between transmissibility and severity of disease, because one of the ways it can become more transmissible is to reproduce in your cells faster so that you shed more virus particles. This also means it takes over quicker and your immune system has less time to respond before it does lots of damage. Whether that outweighs the randomness you describe I don't know. Maybe nobody knows for this virus?

foobiekr 5y ago

In order for this to occur, there needs to be a selection pressure. It doesn't just magically happen. The virus behind Marek's disease in chickens hasn't gotten less severe over time, it's gotten much, much more severe, as an example. HIV does not seem to have gotten less severe, nor smallpox.

mariodiana 5y ago
The virus behind Marek's disease in chickens got much more severe because of the leaky vaccine used on chickens. Here's some introductory material: https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous https://www.nationalgeographic.com/science/article/leaky-vaccines-enhance-spread-of-deadlier-chicken-viruses https://www.youtube.com/watch?v=haRMKsI-jKY And here are a couple of papers: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002198 https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002236
- foobiekr 5y ago
  Yes, Marek's is actually a good illustration of how diseases can go in the other direction.

ikr678 5y ago

That's the theory behind spanish flu mutating into the less severe seasonal flu strains we learned to live with.