How old is he? Has he eaten anything at all? Make sure to give him lots of water to keep his fluids up. You could try liquid foods, such as yoghurt or very mushy vegetables. Does he refuse to eat because it hurts to swallow?
I hope the doctor has given him antibiotics. As was said be sure to have him drink water. As for food you can give him ensure. But, I would let the doctor know that he is not eating. A week is a long time. He may be dehydated and not eating can be a sign of the infection becoming a bigger problem.