Enteric Viruses

Many viruses use the enteric tract as a route of entry to the human, animal or avian host. The onset of acute enteritis is associated with infection by viruses that replicate at or near the site of entry into the intestinal mucosa, including caliciviruses, rotaviruses, adenoviruses, astroviruses, and coronaviruses. These ‘enteric’ viruses occur globally and share similar features. Most are RNA viruses that replicate in the cytoplasm of mature absorptive epithelial cells lining the villi of the small intestine, leading to inflammation and villus atrophy. Vomiting and diarrhea can result in dehydration and death if untreated. Despite abundant growth in vivo, they initially proved difficult or impossible to grow in vitro. Most are genetically diverse, species specific, highly infectious within species and transmitted by the fecal-oral route. Severe symptoms are most commonly associated with primary infections of young animals, and are followed by short-lived immunity. Reinfections are common throughout life, but are often only mildly symptomatic. Safe and effective vaccines have been developed to prevent severe rotavirus disease in young children. In addition to these enterotropic viruses, enteric disease can also result from spread to the intestine of HIV or cytomegaloviruses during the later stages of systemic disease in immunocompromised hosts.