Over a holiday weekend, more than 100 adults at a resort hotel develop a diarrheal illness marked by voluminous, watery stools more than 10 times per day. They also report headaches, abdominal cramping pain, and myalgias. On physical examination, they have manifestations of dehydration and mild fever. Laboratory studies of stool samples show no increase in leukocytes or fat and no RBCs. Their illness lasts just 1 to 3 days and resolves with no sequelae. Which of the following infectious agents is the most likely cause of their illness?

Norovirus outbreaks result from contamination of food or water, most often in venues where multiple persons congregate. Was it the resort pool? Noroviruses, as well as the Giardia parasite, are resistant to chlorination. Was it the buffet? Salads, shellfish, and meats are often implicated. Voluminous diarrhea suggests small intestinal involvement. The lack of leukocytes makes bacterial infection less likely. Cytomegalovirus infections are more likely in immunocompromised persons. Botulism leads to paralysis from a neurotoxin. Staphylococcal food poisoning tends to be abrupt in onset and of short duration. Strongyloidiasis tends to persist for months to years. Cholera produces a life-threatening fluid loss.