Viral Gastroenteritis

Updated: Dec 14, 2014
  • Author: Michael Vincent F Tablang, MD; Chief Editor: Julian Katz, MD  more...
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Overview

Background

Acute gastroenteritis is a common cause of morbidity and mortality worldwide. Conservative estimates put diarrhea in the top 5 causes of deaths worldwide, with most occurring in young children in nonindustrialized countries. In industrialized countries, diarrheal diseases are a significant cause for morbidity across all age groups. Etiologies include bacteria, viruses, parasites, toxins, and drugs. Viruses are responsible for a significant percentage of cases affecting patients of all ages. Viral gastroenteritis ranges from a self-limited watery diarrheal illness (usually < 1 wk) associated with symptoms of nausea, vomiting, anorexia, malaise, or fever, to severe dehydration resulting in hospitalization or even death.

The clinician encounters acute viral gastroenteritis in 3 settings. The first is sporadic gastroenteritis in infants, which most frequently is caused by rotavirus. [1] The second is epidemic gastroenteritis, which occurs either in semiclosed communities (eg, families, institutions, ships, vacation spots) or as a result of classic food-borne or water-borne pathogens. [2] Most of these infections are caused by caliciviruses. The third is sporadic acute gastroenteritis of adults, which most likely is caused by caliciviruses, rotaviruses, astroviruses, or adenoviruses.

For excellent patient education resources, visit eMedicineHealth's Digestive Disorders Center. Also, see eMedicineHealth's patient education article Gastroenteritis.

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Pathophysiology

Viral spread from person to person occurs by fecal-oral transmission of contaminated food and water. Some viruses, like noroviruses, may be transmitted by an airborne route. Clinical manifestations are related to intestinal infection, but the exact mechanism of the induction of diarrhea is not clear.

The most extensive studies have been done with rotavirus. Rotaviruses attach and enter mature enterocytes at the tips of small intestinal villi. They cause structural changes to the small bowel mucosa, including villus shortening and mononuclear inflammatory infiltrate in the lamina propria.

The current knowledge on the mechanisms leading to diarrheal disease by rotavirus is as follows: [3]

  • Rotavirus infections induce maldigestion of carbohydrates, and their accumulation in the intestinal lumen, as well as a malabsorption of nutrients and a concomitant inhibition of water reabsorption, can lead to a malabsorption component of diarrhea.
  • Rotavirus secretes an enterotoxin, NSP4, which leads to a Ca 2+ -dependent Cl - secretory mechanism. Mobilization of intracellular calcium associated with NSP4 expressed endogenously or added exogenously is known to induce transient chloride secretion.

Morphologic abnormalities can be minimal, and studies demonstrate that rotavirus can be released from infected epithelial cells without destroying them. Viral attachment and entry into the epithelial cell without cell death may be enough to initiate diarrhea. The epithelial cell synthesizes and secretes numerous cytokines and chemokines, which can direct the host immune response and potentially regulate cell morphology and function. Studies also suggest that one of the nonstructural viral proteins may act as an enterotoxin, promoting active chloride secretion mediated through increases in intracellular calcium concentration. Toxin-mediated diarrhea would explain the observation that villus injury is not necessarily linked to diarrhea.

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Epidemiology

Frequency

United States

Each year, more than 3.5 million infants develop acute viral gastroenteritis, resulting in more than 500,000 office visits, 55,000 hospitalizations, and 30 deaths. Statistics on sporadic cases of adult viral gastroenteritis are not known; however, food- and water-borne epidemics of viral gastroenteritis are monitored by the US Centers for Disease Control and Prevention (CDC) surveillance programs. The CDC estimates that viruses cause 9.2 million cases of food-related illness each year (out of a total of 13.8 million cases from all causes).

Noroviruses cause approximately 23 million cases of acute gastroenteritis each year and are the leading cause of outbreaks of gastroenteritis. They are responsible for 68-80% of all outbreaks in industrialized countries. The genus Norovirus, formerly called the Norwalk-like virus, is a member of the family Caliciviridae.

Noroviruses are now recognized to be a common cause of gastroenteritis in new settings, including nursing homes and other health care settings, cruise ships, in other travelers, and in immunocompromised patients. [4] In 2010-2011, norovirus was transmitted among players and staff of the National Basketball Association. [5]

In March 2012, the CDC reported a rise in foodborne disease outbreaks caused by imported food in 2009 and 2011. Nearly 50% of the outbreaks implicated food that was imported from regions not previously associated with outbreaks (mostly fish and peppers). Approximately 45% percent of the imported foods causing outbreaks came from Asia. [6]

The frequency is seasonal. The highest incidence of rotavirus cases occurs during the months from November to April. Cruise ship outbreaks of noroviruses are more common during the summer months. However, a CDC study by Tate et al demonstrated a decline in the seasonality of rotavirus following the 2006 introduction of the rotavirus vaccine. [7]

The investigators evaluated data for July 2000 through June 2008 to assess national, regional, and local trends in rotavirus testing and detection and found not only was the onset of the 2007-2008 rotavirus season delayed 15 weeks and the peak delayed 8 weeks relative to the prevaccine rotavirus season from 2000 to 2006, but the 2007-2008 season also lasted a little over half (14 wk) of the median prevaccine seasons (26 weeks). [7] Moreover, there was a 67% decline in the number and a 69% decline in the proportion of 2007-2008 rotavirus-positive test results compared with the median in 2000-2006.

Rotavirus is the most common etiologic agent of health care–acquired diarrhea in pediatric patients. Community- and health care–acquired infections have similar temporal distributions; they are caused by the same viral subtypes; and they affect children of the same age groups. All of the health care–acquired infections with known viral subtypes occurred while the same subtype was still active in the community, suggesting that health care–acquired infections arise from repeated introduction of the community-acquired rotavirus into the hospital setting. [8]

International

Acute viral gastroenteritis is a leading cause of infant mortality throughout the world. By age 3 years, virtually all children become infected with the most common agents. Rotavirus causes 2 million hospitalizations and 600,000-875,000 deaths per year.

Noroviruses were attributed to 9 out of the 21 outbreaks of acute gastroenteritis on cruise ships reported to the CDC's Vessel Sanitation Program from January 1, 2002, to December 2, 2002. The occurrence of noroviruses on cruise ships has led to the use of the term "the cruise ship virus" as another name for these viruses. Some illnesses previously attributed to sea sickness are now recognized to be caused by norovirus infections. [4]

Mortality/Morbidity

Severe cases are seen in the elderly, infant, and immunosuppressed populations, including transplant patients.

Rotavirus infantile gastroenteritis is an important cause of infant mortality in the developing world.

In the United States, elderly persons have the highest risk of death from gastroenteritis.

Caliciviruses may kill more people in the United States than do rotaviruses.

Noroviruses are the most common cause of gastroenteritis in nursing homes, and several such outbreaks have resulted in deaths due to aspiration or exacerbation of another chronic disease. Norovirus infections in hospitalized patients are more severe than those seen in otherwise healthy persons. [4]

The CDC reported enteritis deaths more than doubled in the United States, an increase to 17,000 in 2007 from about 7,000 in 1999. Adults over 65 years old accounted for 83% of deaths. Clostridium difficile (C difficile) and norovirus were the most common infectious causes of gastroenteritis-associated deaths. Norovirus was associated with about 800 deaths annually, though there were 50% more deaths in years when epidemics were caused by new strains of the virus. [9]

Age

See the list below:

  • Acute viral gastroenteritis occurs throughout life. Severe cases are seen in the very young and in the elderly. [10] Etiology also varies with age.
  • In infants, most cases are due to rotavirus.
  • In adults, the most common cause is norovirus.
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