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Abstract: Background: Norovirus (NoV) is the most common cause of acute nonbacterial gastroenteritis outbreaks worldwide, but the impact of NoV infections in Spain remains underestimated. Objectives: This study aimed to determine the prevalence and genetic diversity of NoVs causing outbreaks of acute gastroenteritis in Northeastern Spain (Catalonia) during 2010–2012, and to compare clinical features and levels of viral shedding of the most prevalent GII.4 2012 variant with its predecessor. Study design: NoVs were screened and genotyped in stools from gastroenteritis outbreaks. Genetic diversity over a region covering 50% of VP1, and viral loads were analyzed in stools belonging to GII.4 2009 and 2012 variants. Results: More than 50% of outbreaks were caused by genotype GII.4, although outbreaks caused by multiple strains, GII.6 and GII.1 were also prevalent. During 2012, GII.4 2012 strains clearly replaced GII.4 2009 strains. The first 2012 strain was detected in February 2011, representing the earliest isolate reported worldwide. Epidemiological features of GII.4 2012 and GII.4 2009 outbreaks were comparable, as well as levels of viral shedding in stools. Finally, analysis of the capsid gene showed a higher amino acid variability and diversification in GII.4 2012, affecting sites located at the P2 domain, but also in the shell domain. Conclusions: Clinical features of outbreaks caused by different genotypes circulating in Spain, including outbreaks caused by GII.4 2012 and GII.4 2009 strains, were comparable. Although shed at similar levels than GII.4 2009 strains, GII.4 2012 strains have clearly replaced the previous predominant strain. [Copyright &y& Elsevier]

Objectives: The molecular and epidemiological features of community-based norovirus-associated sporadic gastroenteritis incidents (NASGIs) are poorly understood. This study examined these features and compared the findings with studies of community-based and institutional norovirus-associated gastroenteritis outbreaks (NAGOs). Methods: Fecal specimens from NASGIs and NAGOs that occurred in Victoria, Australia (2002–2007) were tested for norovirus by reverse transcription-polymerase chain reaction methodology. Norovirus genotype was determined by nucleotide sequence analysis. Results: 106 community-based NASGIs, 116 community-based NAGOs and 902 institutional NAGOs were identified. The mean age and gender ratio of individuals associated with community-based NASGIs and community-based NAGOs were similar but differed from that found for institutional NAGOs. Although GII.4 was the predominant genotype associated with all three incident types, the mix of genotypes was similar for community-based NASGIs and community-based NAGOs but that for institutional NAGOs was different. All three incident types had a similar seasonal periodicity due to the pronounced seasonal periodicity of GII.4 incidents. Conclusions: The molecular and epidemiological features of noroviruses associated with community-based NASGIs and community-based NAGOs are similar but are different from those found for institutional NAGOs. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]