Tweedle24 wrote:
"Jools22 I have wondered if the reason so many young people died in the 1918 epidemic was because so many of them had spent the previous four years crammed together up to their knees in mud in the trenches, "
There is an opportunistic element to any invasion by pathogens; germs like an easy life.
To illustrate: lung TB. During recent times when lung TB was endemic it became active with symptoms in people who were undernourished, over crowded, over worked, and so forth. Because TB was widespread the better off people resisted it , became immune, and suffered no symptoms or death from it, Generally speaking.
However covid19 is unlike lung TB as covid19 is so new that nobody worldwide has any acquired resistance. That, together with the general opportunism of all disease germs is why covid19 is pandemic .
As always, the poor people who live in unsanitary rooms, or on the streets, and eat nasty food, and suffer cold and wet, are going to be the worst affected.