Is there a pattern here? (Clue: no, not really)

The Centre for Disease Control lists the main influenza pandemics since 1918.

They happened in:

1918
1957-58
1968
2009

to which we can now add:
2019-20

I always look for patterns in numbers, even if they aren't really there, and that looks like intervals of forty years, ten years, forty years, ten years.

On that basis, said the armchair epidemiologist, the current one will be quite nasty and then we're off the hook for another forty years. That'll see me out nicely. Or perhaps the next big one will finish me off when I'm really old?