Rotavirus strain surveillance in Latin America: a review of the last nine years.

BACKGROUND: Latin America will likely be the first area in the developing world where rotavirus vaccine will be introduced into the routine childhood immunization schedule. In anticipation of that goal, we reviewed the distribution of group A rotavirus genotypes in Latin America to understand the diversity of strains to be targeted by vaccines and to identify novel strains that may pose challenges for vaccines.
METHODS: We reviewed studies characterizing rotavirus strains in Latin America (published in English since 1995) that used molecular methods to type genes encoding the G and P outer capsid proteins, VP7 and VP4, and that reported data on >50 specimens.
RESULTS: Fifteen studies from 5 countries met our criteria. In total, 1989 samples were characterized; 12% (233) were mixed rotavirus infections with more than 1 strain, and 20% (402) were not fully typable. Of the remaining 1354 samples that were fully typed, 83% represented the 4 common strains: P[8],G1 (40%); P[4],G2 (30%); P[8],G3 (6%); P[8],G4 (7%). The unusual strains provide interesting insights into virus evolution: some strains (G5) were regionally common; the emerging G9 strains were widely distributed; many animal-human reassortants were present; and some common serotypes (G3 and G4) were of animal origin. Also an unusual G12 serotype was recently detected in Argentina.
CONCLUSIONS: The common rotavirus serotypes should remain the prime targets for vaccine development. However, the changing profile of rare strains, animal-human reassortants and nontypable strains suggest that rotavirus is constantly evolving. Laboratory surveillance is needed to monitor rotavirus strains now in circulation and to detect those that might escape the immunity induced by vaccines or represent vaccine strains entering the environment.