[magnus]

However, I'm just wondering why it is completely beyond the realm of possibility that people had it prior to that, thinking it was 'worst flu ever,' but never went to hospital and recovered.  Is it because there absolutely would had to have been deaths (at abnormal levels), which would have led to earlier discovery?  That makes intuitive sense, certainly. But is it possible that bad cases, even if they go into the hospital, are never properly diagnosed?  Or is that not possible?

Yes, I believe so.  Not just deaths, but ICU admissions.  Even with a bad flu season, there was no mention of overflowing ICUs.  No overflowing horror stories like we have in NYC, Detroit and we had in Wuhan.  It wasn't until the coronavirus "landed" that we had overwhelmed ICUs within about a month-6 weeks.

[magnus]

However, I'm just wondering why it is completely beyond the realm of possibility that people had it prior to that, thinking it was 'worst flu ever,' but never went to hospital and recovered.  Is it because there absolutely would had to have been deaths (at abnormal levels), which would have led to earlier discovery?  That makes intuitive sense, certainly. But is it possible that bad cases, even if they go into the hospital, are never properly diagnosed?  Or is that not possible?

Yes, I believe so.  Not just deaths, but ICU admissions.  Even with a bad flu season, there was no mention of overflowing ICUs.  No overflowing horror stories like we have in NYC, Detroit and we had in Wuhan.  It wasn't until the coronavirus "landed" that we had overwhelmed ICUs within about a month-6 weeks.