Pediatrics General Considerations - Infectious Diseases a61d5ac5 Most common cause of neonatal diarrhea worldwide is: A Rotavirus B Adenovirus C Norwalk virus D Cholera High-Yield Explanation a. Rotavirus(Ref: Nelson's 20/e p 1616)In early childhood, the single most important cause of severe dehydrating diarrhea is rotavirus infection.