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Viruses are responsible for at least 30–40% of cases of infectious diarrhea in the United States. These agents include rotaviruses; caliciviruses, including noroviruses such as Norwalk virus; astroviruses; enteric adenoviruses; and, less often, toroviruses, coronaviruses, picornaviruses (including the Aichi virus), and pestiviruses. Rotaviruses and noroviruses are responsible for most nonbacterial cases of gastroenteritis.
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Rotaviruses are reoviruses with eight species and significant animal reservoirs. They are the leading worldwide cause of dehydrating gastroenteritis in very young children and are associated with significant morbidity and mortality. Each year, over 200,000 children die of rotavirus infection worldwide. Children aged 6 months to 2 years are the most affected, although adults are affected occasionally as well. By age 5, virtually every child has been infected with this pathogen. The diverse set of rotaviruses (classified by glycoproteins and protease-sensitive proteins [G-type and P-type antigens], which segregate independently) results in a constellation of phenotypes, although only about four of these are responsible for over 90% of disease. Rotavirus infections follow an endemic pattern, especially in the tropics and low-income countries, but they peak during the winter in temperate regions. The virus is transmitted by fecal-oral route and can be shed in feces for up to 3 weeks in severe infections. In outbreak settings (eg, day care centers), the virus is ubiquitously found in the environment, and secondary attack rates are between 16% and 30% (including household contacts). Nosocomial outbreaks are reported.
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The disease is usually mild and self-limiting. A 2- to 3-day prodrome of fever and vomiting is followed by nonbloody diarrhea (up to 10–20 bowel movements per day) lasting for 1–4 days. It is thought that systemic disease occurs rarely, and unusual reported presentations include cerebellitis and pancreatitis. Patients with gastroenteritis are not routinely tested for rotavirus because the results do not alter treatment. If confirmatory testing is required, stool PCR is the most sensitive tool for diagnosing rotavirus. Antigen detection by enzyme immunoassay and the less specific stool examination for viral particles are other options. Oral and intravenous rehydration solutions are the primary treatment options, but effective adjunctive therapies include specific probiotics (eg, Lactobacillus GG or Saccharomyces boulardii), nitazoxanide, diosmectite, or racecadotril. Adjunctive therapies such as oral odansetron shorten the median duration of diarrhea and hospitalization. Local intestinal immunity gives protection against successive infection.
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Vaccines have been highly successful in reducing the global burden of rotavirus. Several rotavirus vaccines exist, and two are available in the United States: a live, oral, pentavalent human-bovine reassortment rotavirus vaccine (PRV, RotaTeq of RV5; to be given at 2, 4, and 6 months of age) and a live, oral attenuated monovalent human rotavirus vaccine (HRV, Rotarix or RV1; to be given at 2 and 4 months of age). The vaccines showed 85–98% efficacy against severe rotavirus gastroenteritis in trials based in the Americas and Europe. Reduced efficacy (50–64%) has been noted in studies conducted in Asia and Africa. One advantage of these vaccines is the ...