Should we pay attention to recombinant norovirus strain GII.P7/GII.6? Dong Xiaogen,Qin Meng,Wang Zhao-E,Yang Xiaoxing,Wu Qingrui,Feng Huiru,Wei Xiuxia,Yu Hong,Li Jinsong,Li Jie Journal of infection and public health BACKGROUND:Recombinant norovirus strain GII.P7/GII.6 has been circulating in Asia and around the world for at least 20 years, but has been responsible for relatively few outbreaks. METHODS:We used statistical analyses, real-time reverse transcription - PCR, and genome sequence analyses to investigate an outbreak of gastroenteritis, identifying the pathogen, the risk factors associated with the outbreak, and the molecular features of GII.P7/GII.6 strains. RESULTS:An outbreak of gastroenteritis was reported at a school involving 12 students and lasting 6 days, from September 13 to September 18, 2017. Epidemiological studies suggested that norovirus was transmitted from person to person and not via contaminated food or drinking water in this outbreak. Using a sequence analysis of the junction region between open reading frames 1 and 2, the pathogen was identified as a recombinant norovirus (strain GII.P7/GII.6). The full-length genome of the outbreak strain shared 86%-97% identity with those of other GII.P7/GII.6 strains. Phylogenetic trees were constructed from partial open reading frame 1 (ORF1) and ORF2 sequences from the outbreak strain and GII.P7/GII.6 norovirus sequences available in GenBank. On the ORF1 tree, the partial sequences of ORF1 were grouped into cluster A (with GII.6), cluster B (with GII.7), and a separate cluster (C), based on the GII.6 and GII.7 reference strains. The ORF2 tree showed all GII.P7/GII.6 strains formed a cluster together with GII.6 strains. Amino-acid substitutions and insertions/deletions were common in the capsid protein, especially in it's P2 and P1 domains. The outbreak was controlled within several days using appropriate measures. CONCLUSIONS:Because it may play a prominent role in future outbreaks, recombinant norovirus strain GII.P7/GII.6 should be monitored with routine surveillance. 10.1016/j.jiph.2018.12.007

Norovirus encounters in the gut: multifaceted interactions and disease outcomes. Mucosal immunology Noroviruses are major causes of gastroenteritis, with epidemic outbreaks occurring frequently. They are an important global health concern, especially for pediatric and immunocompromised populations, and are challenging pathogens to target immunologically due to their rapid rates of genetic and antigenic evolution and failure to stimulate durable protective immunity. In this Review, we summarize our current understanding of norovirus pathogenesis, noting the prominent role of murine norovirus as a small animal model for norovirus research. We highlight intriguing data supporting the possible involvement of norovirus in sequelae including irritable bowel syndrome and inflammatory bowel diseases, and describe the innate and adaptive immune mechanisms involved in control of both human and murine norovirus infection. Furthermore, we discuss the potential implications of recent discoveries regarding norovirus interactions with the gut microbiota, and briefly detail current understanding of noroviral evolution and its influence on viral pathogenesis. Our mechanistic understanding of norovirus pathogenesis continues to improve with increasing availability of powerful model systems, which will ultimately facilitate development of effective preventive and therapeutic approaches for this pathogen. 10.1038/s41385-019-0199-4

Norovirus outbreaks in Beijing, China, from 2014 to 2017. Gao Zhiyong,Liu Baiwei,Yan Hanqiu,Li Weihong,Jia Lei,Tian Yi,Chen Yanwei,Wang Quanyi,Pang Xinghuo The Journal of infection OBJECTIVES:Noroviruses are a leading cause of acute gastroenteritis (AGE) outbreaks worldwide. This study examined the epidemiology and genetic characteristics of norovirus outbreaks in Beijing, China. METHODS:Epidemiological data and fecal specimens were collected through the AGE outbreak surveillance system in Beijing. GI and GII genogroup noroviruses were detected and genotyped. The data were analyzed using descriptive statistics. RESULTS:Between September 2014 and August 2017, 762 AGE outbreaks were reported in Beijing, of which 661 (86.7%) were laboratory-confirmed as norovirus. Most norovirus outbreaks were reported during the spring (66.9%, 442/661), occurred in kindergartens and elementary schools (92.3%, 610/661), and were caused by GII genogroup noroviruses (95.6%; 632/661). The genotypes of the norovirus strains were determined in 468 outbreaks, and GII.P16-GII.2 and GII.P17-GII.17 strains were the most commonly identified. GII.P17-GII.17 and GII.P16-GII.2 strains predominated in 2014-2015 and 2016-2017 outbreaks, respectively. GII.P16-GII.2 noroviruses were responsible for a steep increase in AGE outbreaks in Beijing: 549 norovirus outbreaks were reported from 2016 to 2017, 9.2 times the number that occurred during the previous year. CONCLUSIONS:Norovirus causes a large disease burden in Beijing, and the prevalence of non-GII.4 noroviruses presents a new challenge for the development of vaccines. 10.1016/j.jinf.2019.05.019

The resurgence of the norovirus GII.4 variant associated with sporadic gastroenteritis in the post-GII.17 period in South China, 2015 to 2017. Xue Liang,Cai Weicheng,Gao Junshan,Zhang Le,Dong Ruimin,Li Yonglai,Wu Haoming,Chen Moutong,Zhang Jumei,Wang Juan,Wu Qingping BMC infectious diseases BACKGROUND:Human norovirus is regarded as the leading cause of nonbacterial acute diarrhea in developing and developed countries. Among all genotypes, GII.4 has been the predominant genotype, but in East Asia, it was replaced by the GII.17 in 2014/2015. However, after the prevalence of new GII.17 variant in South China, a sharply increase in the number of norovirus infections associated with sporadic acute diarrhea was detected. In this study, we would investigate the prevalence and genetic diversity of noroviruses in the sporadic acute gastroenteritis cases in the post-GII.17 period in South China. METHODS:Norovirus was screened from 217 patients with sporadic acute gastroenteritis from August 2015 to October 2017 by reverse transcription-polymerase chain reaction. Then, two regions including the partial RNA polymerase and the capsid gene of positive samples were amplified and sequenced. Phylogenetic analyses were performed to determine norovirus genotypes. Complete VP1 sequences of GII.4 strains detected in this study were also amplified and subjected into evolutionary tracing analyses. RESULTS:A total of 43 (19.82%) norovirus samples were confirmed from 217 stool specimens, and it was found that GII.4 resurged as the new predominant variant, accounting for 76.74% (33/43) of positive samples. Only one local strain GZ2015-L550 was clustered with the contemporary GII.P16/GII.4-2012 recombinant variant, and other 32 local strains belonged to the clade with the GII.Pe/GII.4-2012 variant. Other genotypes including GII.17 (n = 4), GII.3 (n = 4), GII.8 (n = 1) and GI. 6 (n = 1) were also detected. Furthermore, all GII.4 strains were phylogenetic analyzed based on their capsid P2 subdomains. Combined with other reported 754 strains, the GII.4-2012 variant could be divided into two clades. Most GII.4 strains collected in 2016 and 2017 in this study (7/8) formed a new cluster A in Clade II with additional 103 contemporaneous strains. In addition, evolutionary tracing of the capsid P2 subdomain of this variant was also analyzed, and one specific amino acid substitutions (N373) was identified for Cluster A. CONCLUSION:In summary, this study confirmed a norovirus infection peak in the post-GII.17 period in South China, which was caused by the resurgence of the GII.4 variant. 10.1186/s12879-019-4331-6