My dad was sick 6 weeks ago and ever since then he does not eat or drink enough. Is the normal?

He has stopped eating and when asked to do so says he does not feel like it. He has lost a lot of weight he has been in hospital on a drip last night but is back at the home. He sleeps a lot of the time but up until 6 weeks ago when we were told he had a virus he has gone down hill since then and stopped eating after that. Will he ever eat again? if anyone can help me understand this or has gone through this i would like to know. We all want to help him but he does not want to eat but will drink some. This has taken place very quickly as he was healthy until then. Now he has lost 2 stone has had blood tests exray the lot all normal. What can we do?