Viral agents of gastroenteritis: public health importance and outbreak management

Morbidity and Mortality Weekly Report, April 27, 1991

Summary

Each year, infectious gastroenteritis causes >210,000 children in the United States to be hospitalized and 4-10 million children to die worldwide. Since the mid-1970s, knowledge has increased dramatically concerning the viral agents that are responsible for much of this public health burden. Rotavirus, the most common cause of diarrhea among children, infects virtually every child in the United States by the age of 4 years and causes potentially lethal dehydration in 0.75% of children <2 years of age. Other recently identified pathogens include the enteric adenoviruses, calicivirus, astrovirus, and the Norwalk family of agents. Conclusive diagnosis of these viruses requires electron microscopic examination of stool specimens, a laboratory technique that is available only at a few large centers, including CDC. Stool samples from an outbreak that are submitted to CDC for detection of viral pathology should be collected in bulk from 10 ill persons during their first 48 hours of illness, while feces are still liquid, and should be stored at 4 C (not frozen). Acute- and convalescent-phase serum samples should be collected from the same persons, plus from an equal number of controls, during the first week of illness and 3 weeks thereafter. Control measures for outbreaks of viral gastroenteritis should focus on the removal of an ongoing common source of infection (e.g., an ill food handler or the contamination of a water supply) and on the interruption of person-to-person transmission that can perpetuate an outbreak in a population after the common source has been removed. Because improvements in environmental hygiene may not be accompanied by reductions of endemic diarrhea caused by viruses, immunization may play an important role in future control; vaccine trials for rotavirus are in progress. In anticipation of vaccine development and use, CDC recently began national surveillance for the viral agents of gastroenteritis, Health-care facilities involved in the detection of rotavirus or the other viral agents of diarrhea can participate.

INTRODUCTION

The public health burden of infectious diarrhea is substantial, particularly among children, both in the United States and worldwide. Each year in the United States >210,000 children <5 years of age are hospitalized for gastroenteritis for an average of 4.5 days, at an annual inpatient cost of almost $1 billion (1). During the period 1973-1983, an average of 500 children in the United States died from diarrhea each year (2). Also, 25 work or school days/100 children are lost each year as a result of acute gastroenteritis (3), and approximately 14% of children in the United States are treated by a physician for rotavirus diarrhea alone (CDC, unpublished data). Worldwide, 3-5 billion cases of diarrhea occur, causing 5-10 million deaths annually (4). Until the 1970s, diagnostic techniques for infectious diarrhea were limited to bacteria and protozoa, and an etiologic agent could be identified in a limited proportion of cases. Investigators had hypothesized, however, that viruses might account for many of the cases of unknown etiology. In 1972, in the examination of stool specimens, electron microscopy identified the Norwalk agent, the most common viral cause of gastroenteritis outbreaks among adults. In 1978, the same technique was used to detect rotavirus, the most common cause of severe diarrhea in children. Since that time, knowledge about these and other more recently discovered pathogens has increased dramatically. Unfortunately, diagnostic technology is insufficiently developed to permit determining the disease burden of each of the known viral pathogens. Even when diagnostic efforts are pursued aggressively, an agent cannot be identified for almost half of diarrheal cases (5).

Current priorities in enteric viral research include: 1) improving diagnostic capabilities for known pathogens to determine their endemic importance and their role in outbreaks; 2) identifying new agents for the 50% of diarrhea cases that are still of unknown etiology; and 3) determining the modes of transmission and the means to prevent disease, including the characteristics of natural immunity and effective vaccines.

As a result of rapid progress in these areas, etiologic identification may soon be possible in most cases of diarrhea, and within a few years a rotavirus vaccine may be licensed. Thus, public health and other health-care professionals should be familiar with the viral agents of gastroenteritis, their role in endemic disease, methods of diagnosis, and measures to manage outbreaks.

This document was prepared by the Viral Gastroenteritis Section, Respiratory and Enterovirus Branch (REB), Division of Viral and Rickettsial Diseases (DVRD), Center for Infectious Diseases (CID), and is intended primarily for the use of state and local health departments who investigate outbreaks. It may also be of use in academic settings, research groups, or other groups interested in studying outbreaks of gastroenteritis.

PATHOGENS: EPIDEMIOLOGIC AND CLINICAL FEATURES

Rotavirus Endemic disease

Rotavirus is the most common cause of severe diarrhea among children. In the United States, approximately 3.5 million cases occur each year. A child has a 2% lifetime chance of being hospitalized for rotavirus diarrhea, which accounts for 35% of diarrheal hospital stays (1 ) and an estimated 75-125 childhood deaths annually (2). Worldwide, an estimated 140 million cases occur each year, causing almost 1 million deaths 6).