causes of frequent diarrhea in adults
1 Norovirus (for example, Norwalk virus, caliciviruses) is the most common cause of epidemics of diarrhea among adults and school-age children (for example, cruise ship infection, schools, nursing homes, day care facilities, and restaurants). 2  Adenovirus infections are common in all age groups.
1 Diarrhea is one of the most common illnesses in all age groups and ranks along with the common cold as a main cause of lost days of work or school. 2  People of all ages can suffer from diarrhea, and the average adult has one episode of acute diarrhea per year, and young children average two acute episodes per year.