From wikipedia:

> It infected 500 million people around the world,[2] or about 27% of the then world population of between 1.8 and 1.9 billion, including people on isolated Pacific islands and in the Arctic. The death toll is estimated to have been 40 million to 50 million, and possibly as high as 100 million

Ok, if it infected 27% of 1.9 billion, that’s 500M people infected.

50-100M of those die, for a fatality rate of at 10 to 20%, not the 2% referenced in OP.

You're nitpicking for no reason; they're close approximations. maybe it was 2.1% or 1.9% maybe it was 40 million or 60 -- record keeping 1918 globally may not have been exactly computer-perfect. There was a war being recovered from, the world was still poor, and medical science inexact.

The GP's point stands, I think.

It’s not 1.9% or 2.1%, the fatality rate would have to be 10% for those numbers to work.

Hypothesis: some were infected, survived, then reinfecterd and died.