OVERVIEW OF VIRAL GASTROENTERITIS

Diarrheal illnesses in humans have been recognized since antiquity. Su ch illnesses continue to take a great toll of lives, with a disproport ionately high mortality in infants and young children in developing co untries. Bacteriologic and parasitologic advances made during the past century led to the discovery of the etiology of some of the diarrheal illnesses, but the etiology of the major portion remained unknown. It was assumed that viruses caused most of these illnesses because: (i) bacteria were recovered from only a small proportion of episodes, and (ii) bacteria-free filtrates were found to induce gastroenteritis in a dult volunteer studies. However, an etiologic agent could not be recov ered despite the ''golden age'' of virology in the 1950's and 1960's w hen tissue culture technology enabled the discovery of numerous cultiv atable enteric viruses, none of which emerged as an important etiologi c agent of gastroenteritis. The discoveries of the Norwalk virus in 19 72, and of rotaviruses in 1973, both without the benefit of in vitro t issue culture systems, ushered in a new era in the study of the etiolo gy of viral gastroenteritis. The Norwalk virus was found to be an impo rtant cause of non-bacterial epidemic gastroenteritis in adults and ol der children, and rotaviruses were shown to be the single most importa nt etiologic agents of severe diarrheal illnesses of infants and young children in both developed and developing countries. With the major a dvances in the study of rotaviruses, there is a high degree of optimis m that in the not-too-distant future, a rotavirus vaccine will be avai lable. In addition, the recent molecular biologic advances in the stud y of the Norwalk and Norwalk-like viruses, now firmly established as c aliviviruses, represent a major new horizon in the study of these viru ses.