I picked up a norovirus-type illness years ago while travelling and it almost ruined my vacation. I was never so intensely ill in such a short period of time. I can see how it can be dangerous to the very young and elderly. It was terrible.
I got it about 3 years ago...me and my entire family (except my 2 year old daughter). I've never been so sick in my life. I had stayed at work overnight and it hit in the middle of the night. It was absolute TORTURE trying to make the 45 minutes drive home...and by the time I got home everyone was sick.
It was a sight with everyone so sick they couldn't move...and my daughter wondering around the house. I had tried to get up and get something to drink. I made it half-way to the kitchen...then laid on the floor for a couple of hours.
HORRIBLE. I can't image anything being worse.