eMedicine Specialties > Gastroenterology > Intestine

Gastroenteritis, Viral

Author: Michael Vincent F Tablang, MD, Resident Physician, Department of Internal Medicine, University of Connecticut Health Center
Coauthor(s): Michael J Grupka, MD, Physician, Atlanta Center for Gastroenterology; George Y Wu, MD, PhD, Professor, Department of Medicine, Director, Hepatology Section, Herman Lopata Chair in Hepatitis Research, University of Connecticut School of Medicine
Contributor Information and Disclosures

Updated: Dec 21, 2009

Introduction

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 eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education article Gastroenteritis.

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 Ca²⁺ -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.

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

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.⁵  

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).⁵ 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.⁶

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

Age

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

Clinical

History

The clinical spectrum of acute viral gastroenteritis ranges from asymptomatic infection to severe dehydration and death. Viral gastroenteritis typically presents with short prodrome, with mild fever and vomiting, followed by 1-4 days of nonbloody, watery diarrhea. Viral gastroenteritis is usually self-limited.

• The history should focus on severity and dehydration. The onset, frequency, quantity, and duration of diarrhea and vomiting are important factors in assessing the status. Oral intake, urine output, and weight loss are important considerations. Viruses are the suspected cause of acute gastroenteritis when vomiting is prominent, when the incubation period is longer than 14 hours, and when the entire illness is over in less than 3 days. Travel history (including cruise ships), eating history, and daycare history are important epidemiological factors.
• A viral cause should be suspected when the warning signs of bacterial infection (ie, high fever, bloody diarrhea, severe abdominal pain, >6 stools/24 h) are absent and an alternative diagnosis is not suggested by epidemiologic clues from the history (eg, travel, sexual practices, antibiotic use).
• Factors associated with severe and prolonged disease are immunodeficiency and immune suppression, comorbid disease, and malnutrition.
• Death results from dehydration and acidosis.
• Ruling out other diagnoses is important.  Mucus or overt blood in the stool almost always indicates bacterial or parasitic infection.

In 1982, the Kaplan criteria were established to distinguish outbreaks due to norovirus from outbreaks of bacterial etiology.  The criteria are highly specific (99%) and moderately sensitive (68%).  The 4 criteria indicative of an outbreak due to norovirus are as follows:⁷

• Vomiting in 50% of affected persons in the outbreak
• Mean incubation period of 24-48 hours
• Mean duration of illness of 12-60 hours
• Lack of identification of a bacterial pathogen in stool culture

Physical

The physical examination can be helpful in determining the etiology of gastroenteritis and in assessing the presence and degree of dehydration.

• Temperature, blood pressure and pulse, and body weight can provide evidence of severity of the condition.
• Temperature may be slightly elevated. High fever suggests bacterial infection. Tachycardia, thready pulse, and hypotension suggest severe dehydration.
• The degree of weight loss may be related to dehydration and the duration of the diarrhea.
• The mucous membranes and the skin should be examined carefully. Dry mouth, no tears, skin tenting, dry skin, and capillary refill are all signs of dehydration.
• The mental status in elderly patients and infants may be abnormal, especially when blood pressure and circulation are compromised.
• The abdominal examination may demonstrate mild tenderness. Severe abdominal pain and tenderness suggest bacterial infection or an abdominal emergency.

Causes

• Sporadic infantile viral gastroenteritis
  • Group A rotavirus causes 25-65% of severe infantile gastroenteritis worldwide.
  • Acute infections with group C are quite frequent in the United States and worldwide.
  • After rotavirus, the most important cause of acute infantile gastroenteritis probably is calicivirus infection. Seroepidemiologic studies have shown that antibodies to caliciviruses are present in 50-90% of children younger than 2 years in Kuwait, Italy, Kenya, China, London, and South Africa. Using broadly reactive reverse-transcription polymerase chain reaction for calicivirus to study stool specimens from children with acute gastroenteritis, studies have found these viruses in 7-22% of cases.
  • Astrovirus infection is associated with 2-9% of cases of infantile gastroenteritis worldwide, making it the third most frequent cause after rotavirus and calicivirus. The burden of astrovirus disease in developing countries might be especially high.
  • Researchers have recognized for a long time that certain enteric adenoviruses are an important cause of infantile gastroenteritis. Studies confirm that they cause 2-6% of cases.
• Epidemic viral gastroenteritis
  • Most cases of epidemic viral gastroenteritis in adults and children are caused by the caliciviruses. Some examples include Norovirus (formerly called Norwalk-like viruses), genogroup I (eg, Norwalk, Southampton, Desert Shield, Cruise Ship); Norovirus (formerly Norwalk-like viruses), genogroup II (eg, Snow Mountain, Mexico, White River, Lordsdale, Bristol, Camberwell, Toronto, Hawaii, Melksham); and Sapovirus (formerly Sapporo-like viruses), which sometimes are referred to as genogroup III, although they are not like Norwalk (eg, Sapporo, Parkville, Manchester, Houston, London).
  • Modern molecular diagnostic techniques, such as broadly reactive reverse-transcription polymerase chain reaction, have linked these viruses to epidemics associated with oysters, contaminated community water supplies, restaurant food, hospital patients and staff, day care facilities, nursing homes, college dormitories, military ships, cruise ships, and vacation spots.
  • Rotavirus and astrovirus also may cause epidemics of viral gastroenteritis.
• Sporadic adult viral gastroenteritis
  • Few studies have examined the causes of sporadic cases of adult viral gastroenteritis.
  • Seroepidemiologic evidence suggests that the etiologies are (in descending order of frequency) caliciviruses, non–group A rotavirus, astrovirus, and adenovirus.

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