People often ask about health out of politeness. This is a very common way to begin a conversation.
1. A: Where's Tony this evening?
B: He's a little under the weather.
A: Really! What's the matter with him?
B: He has the flu.
A: Tell him I was asking about him.
B: I will.
2. A: I haven't seen Bob lately. How is he?
B: He's still pretty sick.
A: That's too bad. What does he have?
B: We don't know, but he's going to see a doctor tomorrow.
A: Let me know if there's anything I can do.
B: Thanks a lot. I'll tell him.