Chapter 122. Acute Infectious Diarrheal Diseases and Bacterial Food Poisoning (Part 6) Table 122-3 Epidemiology of Traveler's Diarrhea Etiologic Agent Approximate Percentage of Cases Comments Enterotoxigenic Escherichia coli 15–50 Single most importan t agent, particularly in summertime in semitropical areas; percentage of cases ranges from 15% in Asia to 50% in Latin America Enteroaggregative E. coli 20–35 Emerging enteric pathogen of worldwide distribution Shigella and enteroinvasive E. coli 10–25 Major causes of fever and dysentery Salmonella 5–10 Causes fever and dysentery Campylobacter jejuni 3–15 More common in winter in semitropical areas; more common in Asia Aeromonas 5 Important in Thailand Plesiomonas 5 Related to tropical travel and seafood consumption Vibrio cholerae 0–10 Most common in India and Asia; also common in Central and South America Rotavirus and 10–40 Latin America, Asia, and Africa; norovirus norovirus associated with seafood ingestion on cruise ships Entamoeba histolytica 5 Particularly important in Mexico and Thailand Giardia lamblia <2 Zoonotic reservoirs in northern United States; affects hikers and campers who drink from freshwater streams; contaminates water supplies in Russia Cryptosporidium 2 Affects tr avelers to Russia, Mexico, and Africa; causes large- scale urban outbreaks in United States Cyclospora <1 Affects travelers to Nepal, Haiti, and Peru; contaminates water or food Unknown 20 Illness improves with antibacterial therapy, implicating bacterial diarrhea Source: After Dupont. Location Day-care centers have particularly high attack rates of enteric infections. Rotavirus is most common among children <2 years old, with attack rates of 75– 100% among those exposed. G. lamblia is more common among older children, with somewhat lower attack rates. Other common organisms, often spread by fecal-oral contact, are Shigella, Campylobacter jejuni, and Cryptosporidium. A characteristic feature of infection among children attending day-care centers is the high rate of secondary cases among family members. Similarly, hospitals are sites in which enteric infections are concentrated. In medical intensive-care units and pediatric wards, diarrhea is one of the most common manifestations of nosocomial infections. C. difficile is the predominant cause of nosocomial diarrhea among adults in the United States. Viral pathogens, especially rotavirus, can spread rapidly in pediatric wards. Enteropathogenic E. coli has been associated with outbreaks of diarrhea in nurseries for newborns. One-third of elderly patients in chronic-care institutions develop a significant diarrheal illness each year; more than half of these cases are caused by cytotoxin- producing C. difficile. Antimicrobial therapy can predispose to pseudomembranous colitis by altering the normal colonic flora and allowing the multiplication of C. difficile (Chap. 123). . Chapter 122. Acute Infectious Diarrheal Diseases and Bacterial Food Poisoning (Part 6) Table 122- 3 Epidemiology of Traveler's Diarrhea . Thailand Plesiomonas 5 Related to tropical travel and seafood consumption Vibrio cholerae 0–10 Most common in India and Asia; also common in Central and South America Rotavirus and 10–40. Latin America, Asia, and Africa; norovirus norovirus associated with seafood ingestion on cruise ships Entamoeba histolytica 5 Particularly important in Mexico and Thailand Giardia lamblia