An unusual outbreak of rotavirus genotype G2P[6] during the 2005–2006 epidemic season in Philadelphia

Abstract Most rotavirus gastroenteritis is caused by G1P[8] strains. When G2 infections are encountered, the P type has most often been reported to be P[4]. The purpose of our study was to describe an unusual outbreak of G2P[6] cases. Children presenting to The Children's Hospital of Philadelphia with acute gastroenteritis have been monitored for rotavirus antigen in stool by ELISA (with G-typing if ELISA positive) since 1994–1995. Compared to the last 12 rotavirus seasons before the 2006 introduction of a new rotavirus vaccine, the 2005–2006 season had by far the highest number of evaluable rotavirus infections [ n = 275 from September 2005 through June 2006, of which 261 (95%) were G typed] and the greatest number of G2 cases ( n = 101, 39% of typed strains). Only 16% of G2 strains were associated with P[4], whereas genotype G2P[6] was responsible for 83% of the G2 infections. Eighty-eight percent of the 84 G2P[6] cases occurred in the 60% of patients who were African-Americans, most of whom were urban residents. Among 157 African-American patients, G2 cases ( n = 80; 52%) predominated, including 74 due to G2P[6]. Children