A 5-month-old Hispanic boy, previously healthy, presents to the emergency department (ED) for 5 days of fever, 3 days of diarrhea and rash, and 2 days of vomiting. He had been diagnosed with acute otitis media by his primary care physician 3 days prior to his presentation and started on amoxicillin. The parents brought their son to the ED because of his persistent fever up to 104°F and decreased oral intake. He has no recent travel and no known sick contacts. His immunizations are up to date and he has never been hospitalized. He was born in the United States, full term with an uncomplicated birth history.