Also, while thousands or even millions of dead would be terrible, that isn't the main problem from a logistics standpoint. There will be 10x the number of dead that are seriously ill and require hospitalisation, which will probably completely overwhelm hospitals in most countries. If this does get bad, then looking after the sick, or simply isolating with them, is going to massively change society and potentially wreck the economy.
Governments are moving to draconian measures to limit the spread, but unless the virus somehow vanishes completely they are probably just delaying the inevitable. Once the lock-downs end, the spread may start again or return in the autumn with the colder weather. During the Spanish Flu pandemic in 1918/9, the second wave was far more deadly. It's a very difficult situation.
And it's going to hit societies with more poorly supplied health care systems harder.
Regarding the Spanish Flu, that epidemic is atypical because of how it propagated through the world. It hit early in 1918 and mostly died off
outside the trenches. Inside the trenches however the disease still spread, fast, and soldiers tend to be on the average healthy young men with very strong immune systems.
This meant that unlike most other diseases which actually become
less lethal over time (so as to better spread and infect before the host dies), the Spanish Flu became
more lethal because otherwise it got wiped out early and before transmission.
Combine this with WW1 lasting well into the autumn and many soldiers not returning from the trenches until well into November 1918, as well as the generally closely packed nature of life in the trenches and the need for soldiers to stay at their posts even if they're not in the best shape and, well, you get a breeding ground for a potent disease indeed. And a disease that will have infected a large number of the returning soldiers, who are returning to a home that is not prepared for the disease they are carrying with them.
