zlacker

Not a biologist, this is not a biological question per se - all viruses and bacteria mutate over time during replication. It's a question of statistics rather... When you have 100 infected individuals and a virus that mutates in 1% of infected people (note: this is a random number, no idea what the actual mutation rate of coronavirus is), you'll end up with one mutated version. When you have 100k of infected people, you'll end up with 1k mutations that are spreading out and (essentially) self-selecting. And when you hit 1M of infected people... it's 100k mutations.

That is why it would have been important to keep infection rates down until there's a vaccine - because it is more than likely now that there's a strain of coronavirus somewhere that has a different spike protein and so is not caught by the existing vaccines.

>>mschus+(OP)
But how did one new strain suddenly amass 17 previously unseen mutations?

Normally we should have sampled a number of strains with fewer of the same mutations, shouldn't we?

>>skinke+Q1
Not an expert here, but there probably are many other strains out there with fewer mutations (and some with more). Most of them residual because they don't provide a clear advantage. The reason we know about this 17-mutation one is that this specific one turned out to have such an advantageous infectivity that it's displacing all other strains and becoming the dominant one.

>>jng+15
Thanks.

That would make sense, if it was the 17th mutation that (possibly together with the rest of the mutations) gave it this advantage.

>>skinke+Q1
The problem is most countries don't sample - they put people through a PCR test and then send them off their way. The UK also does somewhat-regular genetic sequencing of positive tests, precisely to spot new mutations.