1998-1999 rotavirus seasons in Juiz de Fora, Minas Gerais, Brazil: detection of an unusual G3P[4] epidemic strain.

An epidemiologic survey on the rotavirus strains causing gastroenteritis in young children was conducted in Juiz de Fora, Minas Gerais, in Southern Brazil during two consecutive seasons. Rotavirus was detected in 94 of the 1,056 fecal specimens collected from January 1998 to December 1999. Among the 13 discernible long electrophoretic profiles found, one was highly prevalent (73.4%) and represented the rotavirus strain responsible for the May-August winter epidemic outbreak of 1998, as clearly shown in a three-dimensional graph. This epidemic strain, designated JF98, was characterized as subgroup II and genotype G3P[4] by the original reverse transcription-PCR typing assays. Besides the unusual combination of G and P types, this G3 strain lacked reactivity with anti-G3-specific monoclonal antibodies and presented an uncommon pattern upon digestion of its cDNA-copied VP7 gene with the BstYI restriction enzyme. Strain JF98 affected primarily 6- to 24-month-old children and accounted for 85.5% of the severe rotavirus-associated dehydrating diarrhea cases that required hospitalization. As in our previous studies in neighboring Rio de Janeiro and São Paulo, a remarkably large proportion (44%) of mixed infections was detected, generating a complex set of circulating strains in the community, represented by the many distinct electropherotypes. Other common human types were detected as minor strains in single or in mixed infections, including the JF98 strain. Those were types G1, G4, G8, G9, P[8], and P[6], but not G2 or G5. One specimen contained a mixture of group A and C rotaviruses.