Epidemiology
Diarrheal disease remains a leading cause of mortality worldwide. Most deaths are in young children in developing countries. A worldwide campaign by the World Health Organization to treat acute diarrhea with oral rehydration therapy is credited with reducing the death toll among children younger than 5 years old from 5 million deaths in 1982 to less than 800,000 in 2011.[4] The majority of these infections are viral in origin.
In industrialized nations including the US, viral gastroenteritis is one of the most common illnesses in all age groups and a major cause of morbidity. Spread among family members is common. It is estimated that nearly every American will have one episode of viral gastroenteritis per year, and of these cases, 450,000 adults and 160,000 children will be hospitalized and more than 4,000 deaths will occur.[5]
Viral gastroenteritis can occur sporadically or as an epidemic. Noroviruses are the most common cause of outbreaks of nonbacterial gastroenteritis in the US.[6][7] They accounted for 12% of sporadic cases of diarrhea in all age groups in developed countries in one study.[8] In the US, norovirus causes an estimated 19-21 million cases of acute gastroenteritis each year, leading to 109,000 hospitalizations and around 900 deaths, mostly in adults ages 65 years and older.[2] Norovirus infection occurs year-round, but is most common in the winter.
The rotaviruses are the leading cause of diarrhea worldwide and spread easily under conditions of overcrowding and poor hygiene; children may become exposed in developing countries and crowded daycare centers.[9] The Centers for Disease Control and Prevention recommends routine rotavirus vaccination of infants in the US. Rotavirus vaccination has resulted in a significant and sustained reduction of disease prevalence in the US; the median annual percentage of tests positive for rotavirus declined from 25.6% in the pre-vaccine period to 6.1% in the post-vaccine period.[10]
Risk factors
Noroviruses are the most common agents isolated from contaminated food or water sources.
Foodborne or waterborne outbreaks of viral gastroenteritis occur annually.[16]
Cases tend to cluster, and airborne transmission can occur with noroviruses and coronaviruses. Outbreaks on cruise ships and in daycare centers are thought to be due to close contact.
Most viruses that cause gastroenteritis are spread by the fecal-oral route from person to person.[17]
Severe dehydrating diarrhea occurs in very old adults.
People infected with HIV tend to develop atypical and prolonged illness.
Organ transplant recipients tend to develop atypical and prolonged illness.
People who have multiple comorbidities are prone to serious complications and should be followed closely.
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