Situation 25.1 Following a County Fair, 160 Persons Complained of Gastrointestinal Symptoms

Situation 25.1
Following a county fair, 160 persons complained of gastrointestinal symptoms. Symptoms included diarrhea (84 percent) , abdominal cramps (96 percent) , nausea (84 percent) , vomiting (82 percent) , body aches (50 percent) , fever (60 percent; median body temperature = 38.3°C) ; median duration of illness 6 days (range 10 hr to 13 days) .
-In Situation 25.1, fecal samples were found to be negative when cultured. The next step in diagnosing the cause of illness would be

A) to begin antibiotic therapy.
B) blood cultures.
C) muscle biopsy.
D) microscopic examination of feces for viruses.
E) microscopic examination of feces for oocysts.