[Pyramus]

Yes, that is correct. I believe the difference is that most of us were exposed to the flu when we were younger, building immunity to the strains that are seasonal.

This is not the case for new strains. There are reports from the 1918 influenza strain that it killed young people over night: Folks went to bed with fever and didn't wake up the next day.

If you had the flu or know somebody who had, it's no joke.