What Causes Constant Tiredness With A Low Immunity?

hi i have a friend who has had a blood viral for over 2 years now. I am not quite sure exactly her symtoms but she picked the virus up in thailand but it only came to light 9 months after she visited there. she is contantly tired and no energy and picks up things because her immune system is so low? Can you help? she has been to consultants and she is on a lot of medication a day. She cannot work or live her life because of this. What do you suggest?