Acute gastroenteritis is common in adults. It can occur in institutional epidemics or epidemics of food-borne illness; in these cases, caliciviruses are the major cause of the condition. When acute gastroenteritis occurs in nonepidemic form, its causes are less clear. It may be due to caliciviruses or to the less common serotypes of childhood gastroenteritis viruses, such as rotavirus, astrovirus, and adenovirus. The pathogenesis of acute viral gastroenteritis is not completely understood. Old evidence suggests that mild villus damage is responsible, but new evidence indicates that active secretion and motility disturbance may be involved in the production of symptoms. Five common viruses can remain latent in gastrointestinal tissues and produce disease many years after initial infection. Two major herpesviruses, cytomegalovirus and herpes simplex virus, cause ulcerative disease of the gastrointestinal tract. This disease occurs in healthy persons but is more common and more severe in immunocompromised patients. Three other viruses--Epstein-Barr virus, human papilloma virus, and human herpesvirus-8--are implicated in benign and malignant proliferative diseases of the gastrointestinal tract. Epstein-Barr virus has been associated with immunoproliferative disease after transplantation and may also cause small-bowel and colonic lymphoma in healthy adults. It causes most AIDS-related lymphomas. Human papillomaviruses cause anorectal condyloma and anal cancer. Human herpesvirus-8 causes gastrointestinal Kaposi sarcoma.
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