Human rotavirus strains belonging to genotype G9 or P[9] were detected in a collection of stool specimens from children with diarrhea in two cities of the state of Rio de Janeiro, Brazil, between March 1997 and December 1999. G9 strains were first detected in April 1997 and remained prevalent until the end of the study, at a frequency of 15.9% (n ؍ 157). A high percentage of VP7 nucleotide (99.0 to 99.5%) and deduced amino acid identity (98.6 to 99.1%) was found between three randomly selected Brazilian G9 strains and the American G9 strain US1205. A novel G9:P[4] genotype combination was detected in addition to G9:P[8] and G9:P[6], demonstrating that this G genotype may undergo constant genetic reassortment in nature. The P[9] rotavirus strains constituted 10.2%, the majority of which were detected between April and July 1997. The RNA electrophoretic migration pattern of the G3:P[9] strains resembled that of AU-1 virus (G3:P3[9]), suggesting a genetic similarity between the Brazilian G3:P[9] strains and the Japanese virus, which is similar to a feline rotavirus genetically.Rotaviruses are the major etiologic agents of infantile diarrhea worldwide (15). Epidemiologic studies have demonstrated that rotavirus serotypes G1, G2, G3, and G4 are the mostcommon types associated with disease globally, and therefore they are the targets for vaccine development (13,15). Recently, unusual rotavirus serotypes and genotypes have been described in association with diarrhea in various parts of the world. These include serotype G5 in Brazil (9, 17); G8 in Malawi (5), Kenya (21), South Africa (34), the United Kingdom (34), Nigeria (1), and Australia (24); and G9 in India (27), the United Sates (28), Bangladesh (36), Malawi (5), the United Kingdom, (4), Australia (25), France (2), and Ireland (22). The P specificity of a rotavirus is usually more conservative than its G specificity; P1A[8] is the most common serotype detected worldwide, followed by P1B[4] and P2A[6] (13). A rotavirus strain belonging to serotype P3 [9] was first identified in Japan and was demonstrated to be closely related to feline rotavirus strains genetically (20,35). The P[9] rotavirus strains have been detected more often in Japan (14, 37) than in other parts of the world such as Venezuela (32), Italy (32), Malaysia (29), Brazil (17), Israel (31), South Africa (33), Guinea-Bissau (7), and the United States (12). The P [9] isolates are most commonly associated with either G1 (K8-like) or G3 (AU-1-like) serotypes, except for one isolate from Guinea-Bissau which bears a G4 specificity (7).One hundred fifty-seven (23%; n ϭ 678) rotavirus-positive stool samples from children under 5 years of age with acute diarrhea (32 inpatients and 646 outpatients) were collected between March 1997 and December 1999, at four centers in the city of Rio de Janeiro, Brazil, and one center in the neighboring city of Niterói in the state of Rio de Janeiro. The five centers are located in areas of distinct levels of sanitation and socioeconomic backgrounds. The presence of rotavir...
