Oxford Model: Coronavirus May Have Already Infected Half of U.K. Population
nymag.com
nymag.com
If the mortality rate really is much lower than generally presumed at the moment, with no antibody tests to actually verify, then it is absolutely possible that this has been creeping up on us for a month or two earlier in the UK and Italy than currently presumed.
Esp. if you consider that 1) most of the fatal or critical cases are elderly and/or with comorbidities and 2) the symptoms are easily confused with other diseases.
It may well be that if we re-examined old case files and could test retroactively we would find a bunch of cases that were misattributed to other causes.
It's impossible to know for sure without antibody tests.