4 ms·

If it went from 100% IFR (original strain) to 80% IFR (Original + Omicron spike) how did it not reduce the severity? Sure it's more severe than Omicron by itsel

If it went from 100% IFR (original strain) to 80% IFR (Original + Omicron spike) how did it not reduce the severity? Sure it's more severe than Omicron by itself so there were other factors as well, but it does seem like a decrease in severity to me.

algon33 4y ago
Because it has Omicron's increased ability to avoid people's immunity. That would result in higher infectivity than just a copy of the wuhan strain, with near the same severity. Note that earlier Sars viruses had even higher severity than Sars Covid 2 (Wuhan strain), but weren't as infective and killed far fewer people. Which implies that a slight reduction in severity for a gain in infectivity is not a worthwhile tradeoff.
- baja_blast 4y ago
  Exactly, for example Ebola has a mortality rate of around 50% but has only killed around 11 thousand people, SARS-CoV2 has less than 1% can has killed 20 million or more. Wild viruses like SARS1 and MERS are poorly adapted towards humans when the spillover happened making it possible to be contained. But SARS2 a which is a Sarbecovirus a family of gastrointestinal viruses some how was able to bind towards human airways with a binding affinity 20 times that for humans than for bats, all while leaving no traceable trail of mutations that researchers could trace back to the intermediate host. For context with SARS1 and MERS researchers were able to find the spill over animal within a few months. But after 3+ years we have yet to find an intermediate animal host. Also before anyone says "It took years to find the source for SARS1", but that is for the original bat virus, the intermediate animal where the cross over to humans happened was found within months. Additionally SARS1 and MERS had a rapid period of mutations as it adapted towards humans which allowed researchers to trace back to the source.
- Izkata 4y ago
  You're confusing "severity" and "infectivity". Increased infectivity is not increased severity. The evidence they have shows reduced severity and an unknown (but theorized increased) infectivity.
thehappypm 4y ago
Errorbars, probably. 80% and 100% might be samples of a true death rate of 90%.
- Izkata 4y ago
  Indeed, beware of round numbers, they tend to indicate very low sample size and very large error range.
xyzzy123 4y ago
The researchers could not be sure of this result before they did it, which is why I believe there's a reasonable case this should be considered GOF work even if the lethality of their chimera (in hu mice) was ultimately less than that of original strain. Furthermore, strictly speaking I don't believe we know the actual severity of this in humans. While it's possible to make a fairly confident guess, surprises are still possible.

algon33 4y ago

Because it has Omicron's increased ability to avoid people's immunity. That would result in higher infectivity than just a copy of the wuhan strain, with near the same severity. Note that earlier Sars viruses had even higher severity than Sars Covid 2 (Wuhan strain), but weren't as infective and killed far fewer people. Which implies that a slight reduction in severity for a gain in infectivity is not a worthwhile tradeoff.

baja_blast 4y ago
Exactly, for example Ebola has a mortality rate of around 50% but has only killed around 11 thousand people, SARS-CoV2 has less than 1% can has killed 20 million or more. Wild viruses like SARS1 and MERS are poorly adapted towards humans when the spillover happened making it possible to be contained. But SARS2 a which is a Sarbecovirus a family of gastrointestinal viruses some how was able to bind towards human airways with a binding affinity 20 times that for humans than for bats, all while leaving no traceable trail of mutations that researchers could trace back to the intermediate host. For context with SARS1 and MERS researchers were able to find the spill over animal within a few months. But after 3+ years we have yet to find an intermediate animal host. Also before anyone says "It took years to find the source for SARS1", but that is for the original bat virus, the intermediate animal where the cross over to humans happened was found within months. Additionally SARS1 and MERS had a rapid period of mutations as it adapted towards humans which allowed researchers to trace back to the source.
Izkata 4y ago
You're confusing "severity" and "infectivity". Increased infectivity is not increased severity. The evidence they have shows reduced severity and an unknown (but theorized increased) infectivity.

thehappypm 4y ago

Errorbars, probably. 80% and 100% might be samples of a true death rate of 90%.

Izkata 4y ago
Indeed, beware of round numbers, they tend to indicate very low sample size and very large error range.

xyzzy123 4y ago

The researchers could not be sure of this result before they did it, which is why I believe there's a reasonable case this should be considered GOF work even if the lethality of their chimera (in hu mice) was ultimately less than that of original strain. Furthermore, strictly speaking I don't believe we know the actual severity of this in humans. While it's possible to make a fairly confident guess, surprises are still possible.