Outbreaks of adult gastroenteritis traced to a single genotype of rotavirus.

Between November 1998 and December 2000, the Centers for Disease Control and Prevention screened samples from 263 outbreaks of gastroenteritis in the United States and identified 3 that were associated with rotavirus among adults. Rotaviruses from each outbreak were further characterized by reverse-transcription polymerase chain reaction. Surprisingly, all specimens were of serotype G2, a strain that is, as determined by high-stringency hybridization analysis, genetically distinct in all 11 gene segments from the other common rotavirus strains in circulation. The unusual coincidence of identification of only G2 strains in these 3 outbreaks of rotavirus gastroenteritis among adults is similar to results from other studies, in which G2 strains were found in association with more-severe disease in children than other rotavirus serotypes and in association with outbreaks of diarrhea among adults in Japan. Although rotavirus infections in adults are relatively uncommon, which indicates that good overall protective immunity exists, the predominance of G2 strains in outbreaks that have occurred in adults suggests that natural immunity to more common strains does not always provide adequate heterotypic immunity to G2 strains. For the rotavirus vaccines under development, special attention may need to be paid to protection against G2 strains.