But honestly, if you only look into people with mild cases, how do you know the virus causes these mildness?
If I pick 1k people with mild cases at random, I will find pretty much any strain that currently is in circulation. How do I know which strain is harmless?
You don’t, but what you are looking for is a virus with a largish deletion in an essential gene. You then go and look for anyone in contact with this person and check them and then expand out to the whole local area. If everyone infected with this strain has a mild illness they you have hit the jackpot.
I think GP's point was that if you have a candidate it would also make sense to use sequences from the hospitalised to try and confirm your strain didn't put them there.
Aka this being one mechanism by which you confirm it is only producing mild illness. There's a limited amount you can find out by asking because nobody knows what strain they had.
You really want to find every single person who has been infected with the mutant strain and find out how sick they got. If you find a mutant that infected 10,000 people and didn’t cause any serious illness then you have a pretty good idea it safe.
I think the point is that you have to sequence people in the hospital as well, otherwise you won't know if that particular strain is safe or not.
If it is a rare strain, how will you know if it's safe? Seems like it would have to be a rare strain with thousands of cases and hospitalizations in that population are extremely rare.
Sampling bias and other confounding factors would be a real problem in this search, at least from a statistical point of view, imo.
I also think finding everyone who has been infected with a strain isn't feasible, at best you are sampling from the population.
You actually want to screen all people in the local area for the strain that may have it. If all the people have had a mild case and none of them are in hospital then you have something special.
Ah, so you first check for a candidate and then check a (somewhat random) group of people infected with that candidate for severity. That sounds sensible. Thanks for updating a stranger from the internet!
If I pick 1k people with mild cases at random, I will find pretty much any strain that currently is in circulation. How do I know which strain is harmless?