Complex sentence: Rotavirus is the most common cause of gastroenteritis in children both in the developed and developing world and viruses cause about 70% of episodes of infectious diarrhea in this age group.
Split into simpler sentences: Rotavirus is the most common cause of gastroenteritis in children and occurs at similar rates in the developed and developing world. Viruses cause about 70% of episodes of infectious diarrhea in this age group.