[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.