Abstract
BackgroundNoroviruses (NoVs) are an important cause of acute gastroenteritis in humans worldwide. To gain insight into the epidemiologic patterns of NoV outbreaks and to determine the genetic variation of NoVs strains circulating in Belgium, stool samples originating from patients infected with NoVs in foodborne outbreak investigations were analysed between December 2006 and December 2010.ResultsNoVs were found responsible of 11.8% of all suspected foodborne outbreaks reported in the last 4 years and the number of NoV outbreaks reported increased along the years representing more than 30% of all foodborne outbreaks in 2010. Genogroup II outbreaks largely predominated and represented more than 90% of all outbreaks. Phylogenetic analyses were performed with 63 NoV-positive samples for the partial polymerase (N = 45) and/or capsid gene (N = 35) sequences. For 12 samples, sequences covering the ORF1-ORF2 junction were obtained. A variety of genotypes was found among genogroups I and II; GII.4 was predominant followed in order of importance by GII.2, GII.7, GII.13, GI.4 and GI.7. In the study period, GII.4 NoVs variants 2006a, 2006b, 2007, 2008 and 2010 were identified. Moreover, phylogenetic analyses identified different recombinant NoV strains that were further characterised as intergenotype (GII.e/GII.4 2007, GII.e/GII.3 and GII.g/GII.1) and intersub-genotype (GII.4 2006b/GII.4 2007 and GII.4 2010/GII.4 2010b) recombinants.ConclusionsNoVs circulating in the last 4 years in Belgium showed remarkable genetic diversity either by small-scale mutations or genetic recombination. In this period, GII.4 2006b was successfully displaced by the GII.4 2010 subtype, and previously reported epidemic GII.b recombinants seemed to have been superseded by GII.e recombinants in 2009 and GII.g recombinants in 2010. This study showed that the emergence of novel GII.4 variants together with novel GII recombinants could lead to an explosion in NoV outbreaks, likewise to what was observed in 2008 and 2010. Among recombinants detected in this study, two hitherto unreported strains GII.e/GII.3 and GII.g/GII.1 were characterised. Surveillance will remain important to monitor contemporaneously circulating strains in order to adapt preventive and curative strategies.
Highlights
Noroviruses (NoVs) are an important cause of acute gastroenteritis in humans worldwide
To gain insight into the epidemiologic patterns of NoV outbreaks and to determine the genetic variation of NoVs strains circulating in Belgium, we analyzed stool samples originating from patients infected with NoVs in foodborne outbreak investigations conducted by the Belgian Scientific Institute of Public Health (IPH)
Despite the fact that NoVs were detected in some food samples, no sequences could be obtained as amplification by conventional reverse transcription (RT)-PCR was unsuccessful
Summary
Noroviruses (NoVs) are an important cause of acute gastroenteritis in humans worldwide. Noroviruses (NoVs) are on the rise as a causative agent of gastroenteritis in humans of all ages and are responsible for approximately 90% of epidemic non-bacterial outbreaks of gastroenteritis in the world. Food-borne transmissions have been estimated to account for 14% of infections due to NoV [2]. Three overlapping ORFs encode the nonstructural (ORF1) and structural (ORF2 and ORF3) viral proteins. The ORF1-encoded polyprotein is cleaved further by the viral proteinase into six mature products including the genome-linked virus protein (VPg), the proteinase and the highly conserved RNA-dependent RNA-polymerase [6]. ORF 2 encodes the major capsid protein (VP1) that contains an N-terminal arm, a shell or S-domain and a protrusion or P-domain. ORF3 encodes for a small minor structural protein of the virion [8]
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