People often ask about health out of politeness. This is a very common way to begin a conversation.
1.A： How's your father been？
B： He's been out of work for a couple of days.
A： What's wrong with him？
B： He has a bad cold.
A： Well， tell him to take it easy and that I hope he feels better.
B： Thanks. I'll tell him.
2.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.
3.A： How's your brother doing？
B： As a matter of fact， he hasn't been feeling too well.
A： I'm sorry to hear that. What's the matter？
B： He has a slight fever.
A： Tell him I hope he's better soon.
B： I'll tell him. Thanks for asking about him.
4.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 the doctor tomorrow.
A： Let me know if there's anything I can do.
B： Thanks a lot. I'll tell him.