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A Multi-Site Study of Norovirus Molecular Epidemiology in Australia and New Zealand, 2013-2014
Kun Lee Lim1,2, Joanne Hewitt3, Alefiya Sitabkhan1
1School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney, Australia.
Background:
Norovirus (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.
Methodology:
Overall, 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.
Findings:
Peaks 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.
Conclusion:
This 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.
Insights
The GII.4 Sydney 2012 norovirus (NoV) variant remained the leading cause of acute gastroenteritis outbreaks in Australia and New Zealand from 2013 to 2014. This study tracked NoV epidemiology and identified diverse recombinant strains.
Area of Science:
- Virology
- Epidemiology
- Public Health
Background:
- Norovirus (NoV) is a primary cause of acute gastroenteritis globally.
- Genogroup II, genotype 4 (GII.4) variants, particularly Sydney 2012, have driven recent epidemics.
- Limited understanding exists regarding NoV diversity and emergence mechanisms.
Purpose of the Study:
- To investigate the molecular epidemiology of NoV-associated acute gastroenteritis in Australia and New Zealand.
- To identify dominant circulating NoV strains and variants between January 2013 and June 2014.
- To analyze the diversity of recombinant NoV strains.
Main Methods:
- Analysis of 647 Norovirus-positive fecal samples from outbreaks and cases using RT-PCR and sequencing.
- Phylogenetic analysis to determine NoV capsid genotypes and temporal dominance of GII.4 variants.
- Identification and classification of recombinant viruses based on ORF1/2 overlap.
Main Results:
- GII.4 Noroviruses were the predominant cause (63.1%) of gastroenteritis, with Sydney 2012 being the most common variant (98.8%).
- Epidemic peaks varied regionally; aged-care facilities and hospitals were common outbreak settings.
- A significant proportion (56.8%) of non-GII.4 viruses were diverse inter-genotype recombinants, with GII.P16/GII.13 being most frequent.
Conclusions:
- The GII.4 Sydney 2012 variant maintained its dominance in Norovirus-associated gastroenteritis in Australia and New Zealand post-2012.
- The study highlights the continued epidemiological impact of specific NoV strains and the emergence of recombinant variants.
