To examine the epidemiology of rotaviruses in Buenos Aires, Argentina, we screened 1,212 stool samples from children with diarrhea in the southern district of Buenos Aires from 1999 to 2003. We identified 187 samples (15.4%) that were positive for group A rotavirus by use of antigen enzyme-linked immunosorbent assay. Among these specimens, 112 were available for typing: 93 (83.0%) were single-type infections, 9 (8.0%) were mixed-type infections with more than one G or P type, and 10 (8.9%) were G and/or P nontypeable. In contrast to the findings in our last study, from 1996 to 1998, genotype P[4], G2 strains were almost completely absent and P[8], G1 and P[8], G4 strains were dominant, representing more than 80% of the G and P types found. Genotypes G2 and G9 were detected in few samples, and type G3 was completely absent. We identified several uncommon genotype G12 strains, representing the first detections outside of Asia and the United States, by sequencing. Using a genotype G12-specific reverse transcription-PCR, we identified eight (6.7%) positive samples for the 1999 to 2003 period. The high degree of sequence identity between recent G12 isolates from Argentina, the United States, and Asian countries suggests a relatively recent introduction(s) of these strains into humans from a common progenitor. The Argentinean G12 strains belonged to genotype P[9], similar to most of the recently described Asian G12 strains. The finding of G12 strains in several other regions of the world raises the possibility that G12 may be emerging globally and suggests that surveillance for this strain should be conducted routinely.
The incidence of human group C rotavirus infections among children and adults in Buenos Aires was evaluated by enzyme linked immunosorbent assays (ELISA) based on recombinant group C VP6 protein (Cowden strain). A total of 976 stool samples taken from patients (ages 6 months to 15 years) with acute diarrhea were tested for the presence of group C rotavirus. Among these, only 10 (1.02%) were group C rotavirus positive by enzyme-linked immunosorbent assay (ELISA) confirmed by absorption with group C VP6 antibodies and by RT-PCR for both VP6 and VP7 genes. The average age (5.86 years) was significantly superior to that in group A-infected patients (1.63 years). Previous exposure to this virus was assessed by detecting specific IgG in sera taken from healthy individuals grouped by age. Of 844 sera tested, 425 (50.3%) were group C IgG positive by ELISA, confirmed by Western blot analysis. The rates of IgG positivity for group A and C rotaviruses during the first years of life indicated that infections with group C are frequent in older children (3-5 years), whereas group A infections are prevalent in infants and young children (6-18 months). This study shows that group C rotavirus infections in Argentine children occur later in life than group A and are relatively common in spite of the low detection rate of this virus.
A survey was conducted for identification of human group C rotaviruses in stool specimens taken from children suffering diarrhea in suburban Buenos Aires regions. Among 90 true negative group A samples as defined by ELISA, RT-PCR and PAGE, five were positive by group C specific RT-PCR (VP7 and VP6 genes) and three of these samples exhibited the characteristic 4-3-2-2 dsRNA pattern of group C rotavirus. These results were further confirmed by electron microscopy and by ELISA for detection of group C VP6 specific antigens. Sequence analysis of the VP7 gene from one of these isolates revealed a 97.3-98.6% nucleotide identity and up to 99.1% protein homology with human group C rotavirus strains found scattered throughout the last ten years in other countries. Conversely, similar analysis performed with porcine strains showed a much lower homology degree both at the nucleotide (75.5% nucleotide identity) and amino acid level (85.5% protein homology). Detection of group C rotavirus in children with acute diarrhea in Argentina extends the identification range of this agent in the region and is consistent with previous reported data that demonstrate a global distribution of this virus.
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