Diarrheal infections.

Infectious agents usually cause diarrhea by invading and damaging the intestinal mucosa or by producing enterotoxins that alter the secretory and absorptive capacities of the intestinal mucosa. Some infectious agents may do both. Physical malabsorption produced by proliferative outgrowth of bacteria or protozoa may also occur. Rotavirus is the most common cause of pediatric infectious diarrhea in the United States. Escherichia coli and Campylobacter species are the most common bacterial agents.