Wars do a lot of things that are bad, but one of the many bad things they do well is spread disease, often new ones. This pandemic of 1918-19 killed between 20 and 40 million people worldwide, far more than the 18 million killed in the war itself. More died in a single year than in the 4 years of the Black Death.
Wars bring together a lot of people, and there are a lot of people on the move. It also wears people out, so their immune systems are depressed, and there are often food shortages that further weaken them. Hence they provide an ideal environment for epidemics and pandemics.
But it was not just the fatalities. Some of those infected recovered, some died, the rest descended into a coma, where they remained locked for decades, while scientists sought a key to bring them back. They were the forgotten victims of the Great War. The story of this was told by Oliver Sachs, in his book Awakenings, made into a film starring Robin Williams and Robert De Niro.
The neurotransmitter L-Dopamine was found to bring people out of their state of suspended animation, and as a medical student I remember seeing films of these frail old people dancing round the hospital wards that had been their homes for decades. But after what seemed like a miraculous recovery, they mostly went into decline. Was it the drug failing or something else?
It seemed it was life.
These patients were revived as old people, but they had mostly gone to sleep as young adults. When they woke up they were without friends, family, they had had their whole lives stolen from them. There is no drug to treat such irreparable loss and despair. It was the saddest dancing I have ever seen, and to this day I cannot decide whether or not it was a kindness to wake them up. Of course they had to try. If not for those victims, but for any in the future who could be spared their fate.