What Causes Fever, Cold, Diarrhoea And Night Sweats?

My husband has been sick with either the flu (had the flu vaccine in October) or a severe case of food poisoning. One week ago, he dined at a restaurant, that night he wasn't feeling well. He had fevers, chill and the next day he woke up with severe, horrible diarrhea that smelled terrible which has lasted for 5 days. His temperature ranged from 104 to 101 for 3 days. HIs fever has ranged from 101-98 for the past few days. Last night, he woke up with the worst night sweats and his current temperature is 96. We see a GI specialist this afternoon. In the meantime, we are concerned about the night sweats and lowered temperature.