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ACUTE GASTROENTERITIS

BACKGROUND

Acute gastroenteritis (AGE) (often termed “diarrheal disease” when the global burden is discussed) is characterized by the sudden onset of diarrhea with or without vomiting. It results from inflammation of the epithelial lining of the gastrointestinal (GI) tract involving any region from the stomach to the colon, most often as a result of infection. The epidemiology, pathogenesis, clinical features, diagnosis, management, and prevention of the major pathogens causing AGE in children are reviewed in this chapter.

Morbidity and mortality from diarrheal disease is disproportionately found in developing countries, where it ranks as the second leading cause of death among children <5 years of age, closely rivaling pneumonia. One in ten deaths during the first 5 years of life, or a total of approximately 800,000 fatalities annually, are attributed to diarrheal disease,1 and the risk of growth faltering increases among survivors.2 Diarrheal diseases also remain ubiquitous in middle- and high-income countries, although the severe consequences have become uncommon. Prior to rotavirus vaccine introduction, 1 in 135 children in the United States experienced a diarrhea-associated hospitalization during their first 5 years of life, resulting in approximately 145,000 annual hospitalizations,3 and 1 in every 915 diarrhea-associated hospitalizations died.4 Rotavirus is the leading cause of pediatric diarrhea worldwide and believed to cause one-third of all diarrheal deaths.5,6 The other etiologic agents of importance differ according to the level of economic development. Cryptosporidium, enterotoxigenic Escherichia coli (ETEC), and Shigella are the next most important agents in the least developed countries,2 while norovirus generally seconds rotavirus in middle- and high-income countries, followed by a varying contribution from other enteric viruses, the classical bacterial agents (nontyphoidal Salmonella [NTS], Campylobacter, Shigella, and Yersinia), and enterohemorrhagic/Shiga-toxin producing E. coli (STEC).

We are experiencing a dramatic shift in the epidemiology of pediatric AGE since two rotavirus vaccines became available and were recommended for routine immunization of all infants by the World Health Organization and the national regulatory authorities of numerous high- and middle-income countries. Vaccine introduction has resulted in substantial reductions in rotavirus-associated and all-cause AGE hospitalizations in both vaccinated infants (direct protection) and unvaccinated individuals (indirect, or herd protection) living in high- and middle-income countries.6 In addition, substantial declines in less severe disease are demonstrated by reductions in office visits for rotavirus AGE.7 Together, these changes translate into large savings of healthcare costs. Moreover, in Mexico and Brazil, reductions in all-cause AGE deaths have been observed.8,9 Because programmatic uptake is lagging in low-resource settings where most severe disease and death occurs, international efforts are focused on accelerated introduction in developing countries. Lower point estimates of vaccine efficacy observed in clinical trials in these settings would predict that vaccine effectiveness during “real life” programmatic use will be less than is seen in wealthier countries; however, with broad coverage, the life-saving potential is predicted to be substantial. That norovirus has become the most common enteropathogen identified in US children hospitalized with AGE since the introduction of rotavirus vaccine10 provides a poignant illustration of the impact ...

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