reply to @ajross:
how would they know someone is asymptomatic? afaik they are mostly testing people who have symptoms , and their contacts (who will have contracted the same , symptomatic strain)
I think in germany they did antibody testing, or PCR of swabs of people who mostly no longer had a live virus infection to sequence. also, it seems the idea has merit; and i havent read about any team looking for this specific method (identify gene deletions and tracing). It certainly doesn't hurt (and doesnt cost much) to try
btw sweden is doing a survey of live infections in stockholm, however i don't think that they sequence the viruses
to @danieltillet:
maybe post about it in reddit on r/covid19, some epidemiologists hang out there for the latest news