[koheripbal]

This is all correct, but the importance here is to combat the misinformed titles everywhere talking about multiple different "strains" going around, as well as that one damn Chinese paper (now retracted) claiming two different strains with different mortality rates.

Put more simply, two samples of virus can be of the same "strain" even if they aren't _exactly_ the same sequence. This is because replication can sometimes make errors on segments of the genome that do not impact functionality - moreover these same irrelevant loop segments are not error-corrected either, so mutations are common - despite not modifying the properties of the virus. These irrelevant mutations are actually very useful for tracking the virus spread.

A virus mutation becomes a different "strain" when the change is meaningful for the viruses interaction with the host or the environment.

SARS-COV2-2 is a type of virus that does error correction (unlike flu), so the rates of mutation are extremely low. This is good news because if means a vaccine will work, and we won't need a yearly one - like the flu.

[dragonwriter]

> A virus mutation becomes a different "strain" when the change is meaningful for the viruses interaction with the host or the environment.

Of course, that also means that detecting different strains is dependent on understanding those interactions and where they differ. If the post-infection cluster of pediatric multisystem inflammatory syndrome in NYC isn't just NYC being better at identifying that effect, it could well be a sign of a different strain with meaningfully different interactions with hosts. (It could still be a variety of other things, too.)

[DanBC]

> If the post-infection cluster of pediatric multisystem inflammatory syndrome in NYC isn't just NYC being better at identifying that effect,

Doctors in the UK were seeing this throughout April, and issued an alert in late April: https://twitter.com/PICSociety/status/1254508725227982848

[koheripbal]

Different groups of doctors around the world are noticing different aspects of the virus. This is normal with a new virus, and does not indicate that there are multiple strains.

[pbhjpbhj]

I know you didn't assert it, but important to keep in mind it doesn't show the contrary either - ie nor does it show it's not [now] multiple strains.

[dragonwriter]

I hadn't seen the UK alert on that, but to be clear my point wasn't that that particular this was an indicator of a different strain, but that something like that, if it turned out to be isolated which wouldn't always be immediately obvious, could be such an indicator that would only be recognizable as such in retrospect.

[lowwave]

For sure. But I think the point the @gewa trying to make is that yes in the strict academic/technical sense it is correct, however in every day English people probably use "strain" to mean Clad. But not everyone is a evolutionary biologist of some sort.

[newacct583]

For sure. But the point of the article is that to non-expert readers, the "every day English" usage people are thinking of is misinforming them!

You are literally nitpicking the wrong people here. They're trying (well, I thought, though clearly not well enough to satisfy HN pedants) to explain the distinction in a way that conveys the fact that there are no known distinct outbreaks with different medical properties. How that's for precision?

[tialaramex]

> This is good news because if means a vaccine will work, and we won't need a yearly one - like the flu.

That's way ahead of the facts. It means we're more likely to be able to develop a vaccine that works and it's more likely we won't need frequent vaccination to be effective.

Vaccine success involves a certain amount of finger crossing, because it's a natural system rather than an engineered one that we're trying to tamper with. If you've ever boggled at a large spaghetti program, the human immune system makes that look like two dozen lines of clearly documented Java by comparison. None of it has to make sense because Mother Nature doesn't care why she only does results, and in the most brutal way possible.

This is why we've got a bunch of different vaccine programmes in different centres. Some of them might work, hopefully at least one does, and hopefully it produces an immunity that lasts a useful amount of time, has minimal side effects and is cheap to produce in bulk. But there aren't any promises without us having way more advanced biotechnology than exists anywhere today.

[newhouseb]

> SARS-COV2-2 is a type of virus that does error correction

What is the biological process that does this? I'd love to learn more.

[pas]

Totally not a molecular biologist, virologist, etc.

Influenza is smaller about 13K nucleotides vs 30K for corona, it mutates about 4 times faster. It can maintain its larger genome basically because it has better tech. (It seems to better integrate with what it can find in host cells.)

"We demonstrate here, at the molecular level, that CoVs have indeed acquired an enzyme able to enhance the overall fidelity, and that this event might have directly promoted the jump in size of CoV genomes"

"Well before the discovery of nsp14-ExoN in the large Nidovirales genomes (22), this observation led to Drake’s visionary proposition that “RNA viruses would have to acquire several host genes and adapt them to RNA substrates to achieve a major reduction in spontaneous mutation rate. The result would be a substantial increase in genome size” "

https://www.pnas.org/content/115/2/E162

https://www.ncbi.nlm.nih.gov/genomes/GenomesGroup.cgi?taxid=...

https://www.ncbi.nlm.nih.gov/nuccore/1798174254

"Specifically, SARS-CoV-2 seems to have a mutation rate of less than 25 mutations per year, whereas the seasonal flu has a mutation rate of almost 50 mutations per year."

https://www.livescience.com/coronavirus-mutation-rate.html

[ianai]

And apparently that mutation already happened

https://www.santafenewmexican.com/news/coronavirus/lanl-find...