Changing distribution of human rotavirus serotypes during two epidemic outbreaks of gastroenteritis in Campinas, S?o Paulo, Brazil, 2003-2004: Detection of G6 strains

BACKGROUND: Rotavirus serotypes G1-G4 and G9 are the most important agents of severe diarrhea in children worldwide. OBJECTIVE: To characterize rotavirus serotypes/genotypes causing two large outbreaks of diarrhea in Campinas, S?o Paulo, during 2003-2004. STUDY: Rotavirus infection was investigated in 328 stool specimens collected from children and adults with diarrhea by PAGE and RT-PCR and further characterized by semi-nested PCR-typing assays. RESULTS: G3P8] (26.1%), G9P8] (18.7%) and G1P8] (17.9%) were the most frequently detected serotypes/genotypes. G1P8] was predominant in 2003, but significantly decreased the following year when G3P8] and G9P8] prevailed. G5P8] was identified in about 9% of the typed specimens from each year consistent with its endemic nature in Brazil for over two decades. The other globally common serotypes (G4P8] and G2P4]), uncommon G-P combinations, and multiple G serotypes were also found. Rarely found in humans, and not previously reported in Brazil, serotype G6 was identified in three specimens obtained from children in 2004. CONCLUSION: Multiple rotavirus serotypes were observed co-circulating in the city with serotype predominance changing between the two-year study. This study provides pre-vaccine baseline information on locally endemic strains that might help analysis of post-vaccine data.