I keep hearing this sentiment, but I cannot square it with the fact that a non-trivial percent of infected people need to be on ventilators for roughly 20 days. If, back in December, 10k people had what we now know as Covid, there would have been dozens of people on ventilators for weeks at a time in January. The average flu patient needing intubation is only on a ventilator for about 5 days. I just don't see a situation where we have dozens of people testing negative for the flu yet requiring a higher level of ICU care and no alarm bells are raised.

My optimistic side wants the truth to be that there are many strains, and the worst one spread in the last few months. This would mean that there are other strains that provide adequate anti-bodies and yet are mild enough to go unnoticed by professionals.