On the Spanish Flu specifically, the evidence indicates most people who died were killed by secondary bacterial infection, not the virus itself[1]. This was the result of a combination of poor hygienic conditions and lack of antibiotics. Considering that, I think what we are witnessing with SARS-CoV-2 is about what the Spanish Flu would look like today.

[1] https://academic.oup.com/jid/article/196/11/1717/886065

Bacterial pneumonia has a 30% death rate these days.

Bubonic Plague is still around, quite deadly if untreated, antibiotics work if given quickly enough (and are used as a preventative measure for contact persons). Large outbreaks are rare.

There's a sci-fi example of this in the TV show Counterpart. Kind of surreal watching it and then becoming a part of a real life pandemic.

What does "non-hypothetical sci-fi" mean? Surely all sci-fi is hypothetical, in that "fi" stands for "fiction"?

I suppose that "hypothetical sci-fi" could be sci-fi that could be written but has never been

Sorry, I misread the comment upthread. I meant to say the show is an instance of an actual sci-fi show that covers the topic.