The emergence and evolution of the novel epidemic norovirus GII.4 variant Sydney 2012

Abstract

Norovirus is the leading cause of acute gastroenteritis with most infections caused by GII.4 variants. To understand the evolutionary processes that contribute to the emergence of GII.4 variants, we examined the molecular epidemiology of norovirus-associated acute gastroenteritis in Australia and New Zealand from 893 outbreaks between 2009 and 2012. Throughout the study GII.4 New Orleans 2009 was predominant; however, during 2012 it was replaced by an emergent GII.4 variant, Sydney 2012. An evolutionary analysis of capsid gene sequences was performed to determine the origins and selective pressures driving the emergence of these recently circulating GII.4 variants. This revealed that both New Orleans 2009 and Sydney 2012 share a common ancestor with GII.4 Apeldoorn 2007. Furthermore, pre-epidemic ancestral variants of each virus were identified up to two years before their pandemic emergence. Adaptive changes at known blockade epitopes in the viral capsid were also identified that likely contributed to their emergence.

Genetic and Epidemiologic Trends of Norovirus Outbreaks in the United States from 2013 to 2016 Demonstrated Emergence of Novel GII.4 Recombinant Viruses

“…Within epitope D, which includes amino acids directly involved in HBGA binding, variability occurred only at position 393. Amino acid fluctuation among these sites reflects those of the GII.4 New Orleans viruses (62). Not surprisingly, there was more sequence variability among GII.4 viruses harboring the GII.Pe and GII.P4 New Orleans polymerases in this study which have been circulating much longer than viruses with the GII.P16 polymerase.…”

Environmental Transmission of Human Noroviruses in Shellfish Waters

“…Changes in the protruding and immunogenic domain of the capsid protein sequence result in the emergence of new variants of the virus based on immunogenic evolution (18). For instance, adaptive changes in the capsid P2 domain may have caused the epidemic emergence of a novel GII.4 variant (Sydney 2012) and its replacement of New Orleans 2009 as the predominant NoV strain in circulation globally (19).…”

Norovirus Infection in Belarus: Occurrence and Molecular Epidemiology

“…As can be expected, the majority of genotyped NoV isolates belonged to the most prevalent GII.4 NoV genotype. To date, within this genotype 6 distinct genovariants with global circulation have been identified, which accounted for 62-80% of NoV infection outbreaks in different countries (13,14). These genovariants include US 1995US /96 (1996 Genotype GII.3 was represented by a single agent that caused an episode of group morbidity during winter 2012; that was the only instance when circulation of this strain was registered in the country.…”

“…In 2009-2013, the major norovirus genotype was GII.4 (58.3% of all genotyped isolates). Genovariant GII.4 2006b circulated in 2009 and 2010, genovariant GII.4 2009 New Orleans -in 2010and 2012. In addition to GII.4, genotypes GII.6 (16.6%), GII.2 (4.1%), GII.3 (2.2%), and recombinant genotypes GII.g-GII.12 and GII.g-GII.1 (10.4% and 8.3%, respectively) circulated in Belarus.…”