Hello there, I am dr.milan an infectious disease specialist answering your question, For viral infection you need not to take medicine against virus as like in bacterial infection. Viral infection is most of time self limiting. Our body develop immunity against that viral infection in 4 days to 1-2 week duration. Till that time you need to take symptomatic treatment like analgesic for fever, pain killer for bodyache and other as you have various symptoms take symptomatic medicine. You have crohns disease so any medicine you take please consult your treating physician after that only take any medicine. Viral fever must go in very few days. Iron is the substance which is responsible for dark stool. It is like an apple, apple when remain open became dark, it contains iron so, same substance is present in your stool so. Dnt worry about that, just take symptomatic treatment. Hope i have given appropriate guidance to you. if you have any query you can consult me anytime. Give me star rating and thank you according to your satisfactory level. Thanking you.