if we have different strains in circulation already, that answers the question as to how some people could get "reinfected" - they've come into contact with multiple strains.

there were only ever two answers to this question - either the testing was in error, or the virus has mutated. it could be a little of both.

but, if there are actually two or more viruses out there and not just one, that's also a big concern for vaccine testing...

if we're basing our vaccines on chinese data, it might not work on the european strain, which appears to be far worse.