4 ms·

What does it mean, “more infectious and less virulent?” Does that mean less dangerous if you catch it?

goalieca 3y ago
> We observed a decrease in COVID-19 disease severity surrogates after the arrival of the Delta variant, coinciding with significantly smaller plaque sizes. The sentence before leads to the claim. Surrogate is the key word here since it’s really hard to directly quantify.
zethus 3y ago
More infectious: easier to spread & catch Less virulent: less harmful when caught
samus 3y ago
Yes, although it's still by definition not a good idea to catch a disease. If it hits you too hard, you stay home, get quarantined, or put into a hospital. But it has to cause at least some reaction in the host, else there wouldn't be any coughing and sneezing to begin with.
- largbae 3y ago
  HSV-1 (cold sores) might be the ultimate example of success, it manages to spread essentially invisibly.
  - deleted 3y ago
    [deleted]
wolfram74 3y ago
On average, yes. This is also the tendency for most diseases, too evolve into a form less destructive to their habitat so it's easier for them to get to new places to infect. Given that this is biology I will note there are surely counter examples and variations on how fast this trend takes place.
- QuantumGood 3y ago
  Strains that infect more hosts outcompete other strains. People are protected themselves from further infection by being less active / more careful. Sure, if they also killed all hosts, they might themselves die, but it's more about infectiousness than lessening virulence, isn't it? Some infectious strains may be more virulent, some not.
- lawlessone 3y ago
  Can they evolve to evade the tests? So many people relied on testing for this disease. More than most others, that it must have created some small selection pressure.
  - braiamp 3y ago
    As long as such evasion is of benefit for its proliferation. If the ones that evade tests and the ones that don't evade transmit at the same rate, it would be irrelevant.
- bugglebeetle 3y ago
  It’s largely a myth that viruses follow this evolutionary path and no such pressure really exists for COVID. It doesn’t kill enough of the population for this to exist and even when it does kill people, it can spread for weeks or months before they die. https://www.mcgill.ca/oss/article/covid-19/do-bad-viruses-always-become-good-guys-end https://www.mcgill.ca/oss/article/covid-19/do-bad-viruses-al...
  - Majromax 3y ago
    There is some pressure in this direction for respiratory illnesses. It's easiest to spread an illness when it's present in the upper airways (and thus easiest to cough/sneeze out), but the illness does more damage to the lungs when it's deep in the tissues. If it were an exclusive choice, evolutionary pressure would tend to push the former, more transmissible route. The literature at least tentatively reports that Covid variants tend to make this shift (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10024278/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10024278/), which partially explains why the variants were more transmissible than Covid!Classic.

> We observed a decrease in COVID-19 disease severity surrogates after the arrival of the Delta variant, coinciding with significantly smaller plaque sizes. The sentence before leads to the claim. Surrogate is the key word here since it’s really hard to directly quantify.

zethus 3y ago

More infectious: easier to spread & catch Less virulent: less harmful when caught

samus 3y ago

Yes, although it's still by definition not a good idea to catch a disease. If it hits you too hard, you stay home, get quarantined, or put into a hospital. But it has to cause at least some reaction in the host, else there wouldn't be any coughing and sneezing to begin with.

largbae 3y ago
HSV-1 (cold sores) might be the ultimate example of success, it manages to spread essentially invisibly.
- deleted 3y ago
  [deleted]

wolfram74 3y ago

On average, yes. This is also the tendency for most diseases, too evolve into a form less destructive to their habitat so it's easier for them to get to new places to infect. Given that this is biology I will note there are surely counter examples and variations on how fast this trend takes place.

QuantumGood 3y ago
Strains that infect more hosts outcompete other strains. People are protected themselves from further infection by being less active / more careful. Sure, if they also killed all hosts, they might themselves die, but it's more about infectiousness than lessening virulence, isn't it? Some infectious strains may be more virulent, some not.
lawlessone 3y ago
Can they evolve to evade the tests? So many people relied on testing for this disease. More than most others, that it must have created some small selection pressure.
- braiamp 3y ago
  As long as such evasion is of benefit for its proliferation. If the ones that evade tests and the ones that don't evade transmit at the same rate, it would be irrelevant.
bugglebeetle 3y ago
It’s largely a myth that viruses follow this evolutionary path and no such pressure really exists for COVID. It doesn’t kill enough of the population for this to exist and even when it does kill people, it can spread for weeks or months before they die. https://www.mcgill.ca/oss/article/covid-19/do-bad-viruses-always-become-good-guys-end https://www.mcgill.ca/oss/article/covid-19/do-bad-viruses-al...
- Majromax 3y ago
  There is some pressure in this direction for respiratory illnesses. It's easiest to spread an illness when it's present in the upper airways (and thus easiest to cough/sneeze out), but the illness does more damage to the lungs when it's deep in the tissues. If it were an exclusive choice, evolutionary pressure would tend to push the former, more transmissible route. The literature at least tentatively reports that Covid variants tend to make this shift (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10024278/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10024278/), which partially explains why the variants were more transmissible than Covid!Classic.