Genome of Emerging Norovirus GII.17, United States, 2014

Gabriel I. Parra

and Kim Y. Green

Author affiliations: National Institutes of Health, Bethesda, Maryland, USA

Abstract

To determine whether the norovirus strain GII.17 recently detected in Maryland, USA, (Hu/GII.17/Gaithersburg/2014/US) is spreading globally, we characterized the genome. High similarity with the norovirus GII.17 that caused recent outbreaks in Asia indicates that the same strain was present in the United States during the 2014–15 norovirus season (winter).

Noroviruses are major pathogens associated with acute gastroenteritis among persons in all age groups. In developing countries, noroviruses are responsible for an estimated 200,000 deaths per year among children <5 years of age (1). These viruses characteristically cause outbreaks in partially enclosed settings such as schools, childcare centers, nursing homes, military facilities, and cruise ships (2).

Noroviruses possess a genome of single-stranded positive-sense RNA that is organized into 3 open reading frames (ORFs). ORF1 encodes the nonstructural proteins required for replication, including the RNA-dependent RNA polymerase (RdRp); ORF2 encodes the major capsid protein (viral protein [VP] 1); and ORF3 encodes the minor capsid protein (VP2) (2). Noroviruses are genetically diverse and are divided into 6 genogroups (GI–GVI) and ≈30 genotypes according to comparison of VP1 sequences. The fact that patients have been sequentially infected with distinct strains suggests a lack of cross-protection among genotypes (3–5). The current norovirus classification system uses a dual nomenclature based on differences in the RdRp (polymerase or P genotype) and the VP1 region (capsid or G genotype) (6). Because noroviruses are prone to recombine within the ORF1/ORF2 junction, strains with different combinations of P and G genotypes can be detected in nature (7).

Although several norovirus strains circulate, for ≈2 decades, GII.4 has been the predominant genotype infecting humans. It has been proposed that GII.4 strains successfully persist and infect humans by the periodic emergence of new GII.4 variants that escape from herd immunity developed against previous variants (8). Recently, increased detection of GII.17 as the predominant outbreak strain in China has been reported (9). In this study, we characterized the genome of a norovirus GII.17 strain recently detected in Maryland, USA, to determine whether the same GII.17 virus is spreading globally.

Dr. Parra is a research fellow at the National Institute of Allergy and Infectious Diseases, NIH. His research interests include epidemiology, genomics, immunology, and development of vaccine, against gastrointestinal viral infections.

Dr. Green is chief of the Caliciviruses Section of the National Institute of Allergy and Infectious Diseases, NIH. Her research is directed toward the prevention and control of acute gastrointestinal disease caused by noroviruses.

Acknowledgment

This research was funded by the Division of Intramural Research in the National Institute of Allergy and Infectious Diseases, NIH.

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Figures

Technical Appendix

. Differences in the major capsid protein among GII.7 noroviruses, phylogenetic relationships among GII.17 noroviruses circulating worldwide, and relationship of Hu/GII.17/Gaithersburg/2014/US with other GII.17 noroviruses. 661 KB

Suggested citation for this article: Parra GI, Green KY. Genome of emerging norovirus GII.17, United States, 2014. Emerg Infect Dis. 2015 Aug [date cited].http://dx.doi.org/10.3201/eid2108.150652

DOI: 10.3201/eid2108.150652