Abstract
BackgroundNorovirus (NoV) is the major cause of acute gastroenteritis across all age groups. In particular, variants of genogroup II, genotype 4 (GII.4) have been associated with epidemics globally, occurring approximately every three years. The pandemic GII.4 variant, Sydney 2012, was first reported in early 2012 and soon became the predominant circulating NoV strain globally. Despite its broad impact, both clinically and economically, our understanding of the fundamental diversity and mechanisms by which new NoV strains emerge remains limited. In this study, we describe the molecular epidemiological trends of NoV-associated acute gastroenteritis in Australia and New Zealand between January 2013 and June 2014.MethodologyOverall, 647 NoV-positive clinical faecal samples from 409 outbreaks and 238 unlinked cases of acute gastroenteritis were examined by RT-PCR and sequencing. Phylogenetic analysis was then performed to identify NoV capsid genotypes and to establish the temporal dominance of circulating pandemic GII.4 variants. Recombinant viruses were also identified based on analysis of the ORF1/2 overlapping region.FindingsPeaks in NoV activity were observed, however the timing of these epidemics varied between different regions. Overall, GII.4 NoVs were the dominant cause of both outbreaks and cases of NoV-associated acute gastroenteritis (63.1%, n = 408/647), with Sydney 2012 being the most common GII.4 variant identified (98.8%, n = 403/408). Of the 409 reported NoV outbreaks, aged-care facilities were the most common setting in both Western Australia (87%, n = 20/23) and New Zealand (58.1%, n = 200/344) while most of the NoV outbreaks were reported from hospitals (38%, n = 16/42) in New South Wales, Australia. An analysis of a subset of non-GII.4 viruses from all locations (125/239) showed the majority (56.8%, n = 71/125) were inter-genotype recombinants. These recombinants were surprisingly diverse and could be classified into 18 distinct recombinant types, with GII.P16/GII.13 (24% of recombinants) the most common.ConclusionThis study revealed that following its emergence in 2012, GII.4 Sydney 2012 variant continued to be the predominant cause of NoV-associated acute gastroenteritis in Australia and New Zealand between 2013 and 2014.
Highlights
Norovirus (NoV) is the leading cause of human viral gastroenteritis globally and responsible for more than half of the gastroenteritis outbreaks that occur annually [1]
NoV infections are known to be the primary cause of institutional gastroenteritis outbreaks [21, 38, 39], which are required by law to be reported to public health authorities, both in Australia and New Zealand
By assessing the number of institutional outbreaks each month and supplemented by the monthly laboratory-confirmed NoV positive cases, we investigated the NoV activity in Australia and New Zealand between January 2013 and June 2014 (Fig 1)
Summary
Norovirus (NoV) is the leading cause of human viral gastroenteritis globally and responsible for more than half of the gastroenteritis outbreaks that occur annually [1]. In developing countries NoV is estimated to kill over 200,000 people annually; mainly children under 5 years old [5]. NoVs infect all age groups, with clinical symptoms commonly characterised by diarrhoea, projectile vomiting, fever and abdominal cramps [2, 6]. Norovirus (NoV) is the major cause of acute gastroenteritis across all age groups. The pandemic GII. variant, Sydney 2012, was first reported in early 2012 and soon became the predominant circulating NoV strain globally. We describe the molecular epidemiological trends of NoV-associated acute gastroenteritis in Australia and New Zealand between January 2013 and June 2014
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