Group IMPORTANCELittle is known about the diversity of cocirculating G2 rotaviruses and how their evolution may undermine the effectiveness of rotavirus vaccines. To expand our understanding of the potential genetic range exhibited by rotaviruses circulating in postvaccine communities, we analyzed part of a collection of rotaviruses recovered from pediatric patients in the United States from 2010 to 2011. Examining the genetic makeup of these viruses revealed they represented three segregated groups that did not exchange genetic material. The distinction between these three groups may be explained by three separate introductions. By comparing a specific gene, namely, VP7, of the recent rotavirus isolates to those from a collection recovered from U.S. children between 1974 and 1991 and other globally circulating rotaviruses, we were able to reconstruct the timing of events that shaped their ancestry. This analysis indicates that G2 rotaviruses are continuously evolving, accumulating changes in their genetic material as they infect new patients.

Background: Recent estimates attribute 527 000 deaths in children less than five years of age to rotavirus diarrhea annually, with 145 000 occurring in sub-Saharan Africa. Human astroviruses have been identified as one of the most frequent causes of infantile diarrhea, second in incidence only to rotavirus. This study was conducted to determine the prevalence of rotavirus and astrovirus and also to establish the circulating strains of rotavirus in a community in Nigeria where most diarrheic patients do not visit clinics or health care centers. Methods: A total of 154 stool samples (134 diarrheic and 20 non-diarrheic) were collected from infants and young children less than 5 years of age from January-March 2002. Samples were obtained by house-to-house visit in randomly selected districts in Zaria, Northwestern Nigeria. The samples were screened for rotavirus and astrovirus antigens using commercially available Enzyme Linked Immunosorbent Assay (ELISA) kits. All positive group A rotavirus samples were further subjected to VP6 sub-group ELISA, Polyacrylamide gel electrophoresis (PAGE) to determine their RNA electropherotypes and Reverse transcription polymerase chain reaction (RT-PCR) to determine their VP7 and VP4 genotypes. Results: Rotavirus and astrovirus antigens were detected in 9% (12) and 5% (7) of the 134 diarrheic stool samples respectively. No viral antigen was detected in the non-diarrheic stools. Rotavirus infection was more common in younger children than astrovirus infection. VP6 sub-group II specificity (58.3%), long RNA electropherotypes (41.6%), VP7 genotype G1 (33.3%) and VP4 genotype P [6] (33.3%) were the most common strains in circulation at that time in the community. Of significance is the fact that a large proportion of the rotavirus strains in circulation could not be assigned either a VP6 subgroup or RNA electrophoretic pattern probably as a result of low viral load. Conclusion: In this community-based study, rotavirus and astrovirus were significantly associated with diarrhea. However, the prevalence of rotavirus infection among children appears to be low while that of astrovirus falls in the range seen in hospital-based studies around the continent. Rotavirus, astrovirus, diarrhoea, children, community, Nigeria Résume Contexte: Des estimations récentes attribuent 527 000 décès annuels d'enfants de moins de 5 ans à la diarrhée par rotavirus, parmi lesquels 145 000 surviennent en Afrique Sub Saharienne. Les astrovirus humains ont été identifiés comme l'une des causes les plus fréquentes de diarrhée infantile, en second lieu viennent les atrovirus. Cette étude a été menée pour déterminer la prévalence des rotavirus et astrovirus et établir les souches circulantes de rotavirus dans une population du Nigéria ou la plupart des patients diarrhéiques ne consultent pas en clinique ni les centres de santé. Key words: Epidemiology of Rotavirus and Astrovirus infection in Nigerian children. Aminu M. et al. Page | 169Méthode: Un total de 154 échantillons de selles (134 diarrhéiques et 20...

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