I would like to refer you to: https://www.cdc.gov/flu/pandem... "It is estimated that about 500 million people or one-third of the world’s population became infected with this virus. The number of deaths was estimated to be at least 50 million worldwide with about 675,000 occurring in the United States. Mortality was high in people younger than 5 years old, 20-40 years old, and 65 years and older. The high mortality in healthy people, including those in the 20-40 year age group, was a unique feature of this pandemic." So fatality rate of 1918 flu looks to be more like 10%. Also interesting that not only old codgers were the hardest hit.

I just want to point out that UTC isn't "astronomical time", which your comment seems to be implying. The timekeeper of UTC is an ensemble of atomic clocks in various locations around the world. The timekeeper of Greenwich Mean Time (GMT) is the rotating earth in orbit around the sun and involves astronomical observations to determine the time. By the way, the GPS has an ensemble of atomic clocks also, separate from UTC. There must be some effort towards harmonizing UTC and GPS time but I am too lazy to look it up.