These DNA viruses (unlike other adenoviruses) could not be cultured using standard virus culture systems. The most frequent are types 40 and 41. These enteric adenovirus species are the second most common cause of severe gastroenteritis in young children (after rotavirus), comprising about 10%-15% of cases (range, 5%-52%). It has also been the second or third most common overall cause of infant gastroenteritis. Diarrhea is the predominant symptom. Vomiting may be present but is less prominent than that seen in rotavirus infection. The gold standard for diagnosis has been EM of stool specimens. However, EM cannot differentiate between fastidious and other adenovirus species. Culture can be done in some cases using nonroutine tissue culture cells. Several EIA tests for virus antigen in stool have been described and one commercial kit for types 40 and 41 is now available. Nucleic acid probes have also been used experimentally.