How long do stomach viral anthems last? I had diarrhea and vomiting on Dec 20th with a 100.6 fever . fever dissipated next day. diarrhea lasted until Sun Dec 24. Sore throat started Dec 21, and got worst on 24, but is now better. However I developed a rash on stomach, chest, and back on 24th. I have had mmr . when I.was little, and no fever since Thursday 20th. when will rash go away, and is it just a viral exanthem?