The Spanish Flu of 1918 killed a lot of young healthy people. I believe it basically threw their immune system into over-drive and killed them. Younger and older people with less vibrant immune systems just got sick and then they got better. Counter-intuitive, but life is like that sometimes.
I had an aunt that died from it. Abt 10 years old. What it did was flood the lungs with so much mucus that they drowned.
The cause of death on her was listed as consumption.
I have had this one for 9 weeks counting this week. So much mucus and coughing all the time. It comes back on you also. I will be fine for a week and then its backwards.
BTW, the Dr. I went to said that they told him that this on is just a small ways to becoming the spanish flu.
There were two major waves of the Spanish Flu. The first hit in the spring of 1918, then again in late summer, at least in the United States. The first round killed mostly the young and elderly, as most flu outbreaks hit these groups the hardest. The second wave killed the healthy and strong, in the cytokine storm you described where the immune system overwhelms the body.
However research is ongoing and the source and mechanism of the pandemic is still being debated. The Wikipedia article I used to check my memory indicates that overcrowding and sanitary conditions may have been to blame.
I find the topic fascinating because the outbreak of the Spanish Flu was like a real zombie apocalypse, or some Twilight Zone episode where the calls of “Bring out your dead” returned from the Middle Ages.