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Acute diarrhea results in substantial morbidity and mortality. Globally, there were an estimated 6.3 billion episodes of diarrheal disease in 2017.1 Among children less than 5 years of age, the incidence is approximately three episodes per person per year, while among older children and adults it is less than one episode per person per year.2 Diarrheal disease is a key cause of childhood mortality. In 2017, the Global Burden of Disease study—a global collaborative effort to understand the burden and causes of morbidity from all causes—estimated that diarrheal diseases resulted in 1.6 million deaths globally, with 533,000 occurring among children less than 5 years old.3 These resulted in 41.4 million Disability Adjusted Life Years (DALY’s) lost, which equates to years of life lost due to ill health, disability, or death.4 Infectious diarrhea is also important for its propensity to spread globally via infected humans and animals and contaminated foods. In countries of all levels of development, there are regular outbreaks of diarrheal disease requiring intervention that are tailored to the pathogen and nature of spread.

This chapter summarizes the major causes of acute diarrhea, the agents responsible, how they are transmitted, and the main public health interventions.


Diarrhea is a common symptom of gastrointestinal infection and is commonly defined as “≥3 or more loose stools in a 24-hour period.”5 The syndrome of acute diarrhea is caused by a range of pathogens that vary in their characteristics of infectiousness, clinical manifestations, and transmission. These pathogens result in different symptoms and duration of illness. For example, norovirus—one of the most common causes of gastroenteritis globally—results in the majority of infected persons experiencing diarrhea less than 48 hours in duration. In fact, many persons infected with norovirus do not even experience diarrhea, but may experience nausea and vomiting alone. In contrast, people infected with bacterial pathogens, such as Shiga-toxin-producing Escherichia coli may experience bloody diarrhea that can progress to serious sequelae including hemolytic uremic syndrome (Table 108-1).


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