Spanish Flu: Epidemiology and pathology (Wikipedia)

> A large factor in the worldwide occurrence of the flu was increased travel. Modern transportation systems made it easier for soldiers, sailors, and civilian travelers to spread the disease.[citation needed] Another was lies and denial by governments, leaving the population ill-prepared to handle the outbreaks.[73]

Sounds just like early 2020

> In civilian life, natural selection favors a mild strain. Those who get very ill stay home, and those mildly ill continue with their lives, preferentially spreading the mild strain. In the trenches, natural selection was reversed. Soldiers with a mild strain stayed where they were, while the severely ill were sent on crowded trains to crowded field hospitals, spreading the deadlier virus

Sounds just like Shelter in place (mild cases, asymptomatic & those who's immune system can fight it stay home, sick people leave home for medical attention)