As I mentioned before, doofi at Oxford have suggested that vast number of people have already contracted coronavirus, and that the fraction of those infected that become ill is thus much smaller than it looks. There was never any chance of this. PCR positivity rates were not high, and in a fast-growing epidemic, most cases would be new enough to be PCR-positive.
Now, a new study shows that this notion is not correct. ” 164 close contacts tested by PCR and serology. 16/164 of contacts PCR+ & all PCR+ also serology+. Additional 7/164 were serology+ but PCR-.”
There are some people that have contracted disease and don’t show up on PCR – but not many.