I do think age has a lot to do with how serious it can be.
some years ago I got camphlobacter (don't know how to spell it) and the infection is so serious the hospital had to report it to the health department so they could figure out how I got it. After I recovered and went back to work, a colleague said, "The newspaper said there was a sudden outbreak of camphlobacter. Three people died."
Well, gee thanks. I needed to hear that. (the infection comes from bad water or diseased chicken. I think I got it from chicken in a restaurant. It was a long time until I would eat chicken again.)
Life in Deludedville: I remember recovering from that infection and thinking, 'I'm better now! I can stand up straight without feeling a sharp pain!" (I couldn't walk yet)
Adding: The reason I didn't die, I believe, is because I pushed back when the clinic kept saying, "It's just a flu. Call us if you're not better in 2 days." I KNEW it wasn't the flu, so I insisted on tests. Why there are more aggressive and asserted people in the world: The passive ones tend to die faster.