@Steel - well, I think the flu is an issue for elderly people.
I caught a really bad strain of flu in summer 2013, when I was 34. I legitimately wondered at one point whether I was dying. My saliva literally burnt my tongue and mouth, and my stomach if I swallowed it. I kept having to spit saliva in the sink, then drinking iced water or cold milk. I asked my dad to drive me to hospital at 6am one morning. He refused, so I walked into A&E. I told the doctor about my saliva and he said it was the flu infection that did this. <--- this did kinda scare me, I gotta say.
If elderly people don't bother with flu jabs, or live in a part of the world that doesn't have them, they could be in real trouble.