I'm not going to help warn someone about a health issue
Why don't you want to warn someone about a health issue?
They are well aware of their own condition, why should I meddle?
You should let them know about their health issue. They may already know, but you just want to make sure so they don't get sicker.
I'm certain they know, but if they don't, they should be punished for it.
No one should be punished because of a health problem. You should warn the person and be empathetic. If you get sick in the future, you will want someone to do the same for you.