First activity is a mingler.
Make pairs and do janken. The winner is the doctor and the loser the patient. The patient calls for the doctor and then does a gesture imitating one of the ailments on the doctor's paper that hasn't been signed yet. The doctor guesses what is wrong and then asks the student to sign their paper and they part company. Its amusing if you play up how odd it is that the doctor doesn't actually try to help the patient. After a time limit see how many signs the students collected.
Before you start practice the vocab a lot. I usually do each gesture and have the students call out what's wrong.
The next is a group activity. The students take turns coming to the teachers and asking the teacher what's wrong. The teacher tells them and they go back to their group to pick advice and bring it back to the teacher. The teacher says thanks and then the next member of their group comes up to do the second dialogue. Each group should have a copy of the advice paper.
Two New Versions
The Shorter version is the same as above but shorten a bit so it fits on one paper.
The No Sign Game is for classes that don't allow mingling. For this one after practicing the vocabulary as a class in pairs they can practice again saying 'what's wrong?' and 'I have a ....'. If you want to make it a game they can do janken. The winner is the doctor and gets to cross out the symptons as their partner speaks them. Also the advice giving is filled in. This way they can complete it all as a writing assignment without having to move around so much.