Molecular and evolutionary characterization of norovirus GII.17 in the northern region of Brazil

Human norovirus in Brazil: an update of reports in different settings

Norovirus is an important etiologic agent of acute gastroenteritis and has become even more relevant in Brazil after the implementation of the monovalent rotavirus vaccine in 2006 through the public health system, now representing a significant portion of the etiology of acute diarrheal diseases. Although diagnosing acute gastroenteritis caused by norovirus is a relatively simple process, and the infection tends to be self-limited, the virus can be considerably harmful to vulnerable populations, such as children, the elderly, and immunocompromised individuals. The spread of norovirus is also particularly favorable among such groups due to its mode of transmission, favored by cluttered environments such as in hospitals and densely populated regions. Additionally, norovirus' ability to spread through water and food creates the need for measures to ensure adequate sanitation and the development of effective measures to prevent outbreaks and severe manifestations of the disease. This review aims to address the main reports of human norovirus detected in Brazil over the years, focusing on clinical-hospital, food-related, and urban conglomerate contexts, including the circulating strains.

Genome characterisation of norovirus GII.P17-GII.17 detected during a large gastroenteritis outbreak in Romania in 2021

Norovirus (NoV) is one of the leading causes of acute gastroenteritis worldwide. Genotype GII.P17-G.II.17 emerged in Asia between 2013 and 2015 and transiently replaced the GII.4 Sydney 2012 variant circulating at that time. We present the genome characterisation of a GII.P17-GII.17 strain causing a large outbreak in Romania in 2021. Our study shows that the 2021 strain belongs to a novel cluster of genotype GII.17, different from the two previously recognised P.17 clusters. Distinctive substitutions in predicted conformational epitopes of VP1 were identified for this new cluster. Also, our phylogenetic analysis showed the existence of another P.17 cluster grouping strains from France and Canada.

Virological and Epidemiological Features of Norovirus Infections in Brazil, 2017-2018

Noroviruses are considered an important cause of acute gastroenteritis (AGE) across all age groups. Here, we investigated the incidence of norovirus, genotypes circulation, and norovirus shedding in AGE stool samples from outpatients in Brazil. During a two-year period, 1546 AGE stool samples from ten Brazilian states were analyzed by RT-qPCR to detect and quantify GI and GII noroviruses. Positive samples were genotyped by dual sequencing using the ORF1/2 junction region. Overall, we detected norovirus in 32.1% of samples, with a massive predominance of GII viruses (89.1%). We also observed a significant difference between the median viral load of norovirus GI (3.4×10⁵ GC/g of stool) and GII (1.9×10⁷ GC/g). The most affected age group was children aged between 6 and 24 m old, and norovirus infection was detected throughout the year without marked seasonality. Phylogenetic analysis of partial RdRp and VP1 regions identified six and 11 genotype combinations of GI and GII, respectively. GII.4 Sydney[P16] was by far the predominant genotype (47.6%), followed by GII.2[P16], GII.4 Sydney[P31], and GII.6[P7]. We detected, for the first time in Brazil, the intergenogroup recombinant genotype GIX.1[GII.P15]. Our study contributes to the knowledge of norovirus genotypes circulation at the national level, reinforcing the importance of molecular surveillance programs for future vaccine designs.

Epidemiology of norovirus gastroenteritis in hospitalized children under five years old in western China, 2015-2019

OBJECTIVES

Norovirus is associated with one-fifth of all gastroenteritis cases, but basic epidemiological data is lacking, especially in developing countries. As long-term surveillance on norovirus gastroenteritis is scarce in western China, this study aims to update the epidemiological knowledge of norovirus gastroenteritis and to characterize the genotypes of norovirus strains.

METHODS

Stool samples were collected from hospitalized children under 5 years old with gastroenteritis in Chengdu, China. All samples were tested for norovirus as well as rotavirus, sapovirus, enteric adenovirus, and astrovirus by real-time RT-PCR. RdRp and VP1 genes were sequenced in norovirus-positive samples to investigate viral phylogenies.

RESULTS

Of the 1181 samples collected from 2015 to 2019, 242 (20.5%) were positive for norovirus. Among norovirus-positive cases, 65 cases had co-infection with another virus; norovirus/enteric adenovirus was most frequently detected (50.8%, 33/65). The highest positive rate was observed in children aged 13-18 months (23.7%, 68/287). Norovirus infection peaked in autumn (36.6%, 91/249), followed by summer (20.3%, 70/345). Pearson correlation analysis showed significant correlation between the norovirus-positive rate and humidity (r = 0.773, P < 0.05). GII.4 Sydney 2012 [P31] (48.5%, 79/163) and GII.3 [P12] (35.6%, 58/163) were the dominant norovirus strains.

CONCLUSIONS

Norovirus has become one of the most common causes of viral gastroenteritis in children under 5 years old in western China. Continuous monitoring is imperative for predicting the emergence of new epidemic strains and for current vaccine development.

Unveiling Viruses Associated with Gastroenteritis Using a Metagenomics Approach

Acute infectious gastroenteritis is an important illness worldwide, especially on children, with viruses accounting for approximately 70% of the acute cases. A high number of these cases have an unknown etiological agent and the rise of next generation sequencing technologies has opened new opportunities for viral pathogen detection and discovery. Viral metagenomics in routine clinical settings has the potential to identify unexpected or novel variants of viral pathogens that cause gastroenteritis. In this study, 124 samples from acute gastroenteritis patients from 2012–2014 previously tested negative for common gastroenteritis pathogens were pooled by age and analyzed by next generation sequencing (NGS) to elucidate unidentified viral infections. The most abundant sequences detected potentially associated to acute gastroenteritis were from Astroviridae and Caliciviridae families, with the detection of norovirus GIV and sapoviruses. Lower number of contigs associated to rotaviruses were detected. As expected, other viruses that may be associated to gastroenteritis but also produce persistent infections in the gut were identified including several Picornaviridae members (EV, parechoviruses, cardioviruses) and adenoviruses. According to the sequencing data, astroviruses, sapoviruses and NoV GIV should be added to the list of viral pathogens screened in routine clinical analysis.

Evolutionary and Molecular Analysis of Complete Genome Sequences of Norovirus From Brazil: Emerging Recombinant Strain GII.P16/GII.4

Noroviruses (NoVs) are enteric viruses that cause acute gastroenteritis, and the pandemic GII.4 genotype is spreading and evolving rapidly. The recombinant GII.P16/GII.4_Sydney strain emerged in 2016, replacing GII.P31/GII.4_Sydney (GII.P31 formerly known as GII.Pe) in some countries. We analyzed the complete genome of 20 NoV strains (17 GII.P31/GII.4_ Sydney and 3 GII.P16/GII.4_Sydney) from Belém and Manaus, Brazil, collected from 2012 to 2016. Phylogenetic trees were constructed by maximum likelihood method from 191 full NoV-VP1 sequences, demonstrated segregation of the Sydney lineage in two larger clades, suggesting that GII.4 strains associated with GII.P16 already have modifications compared with GII.P31/GII.4. Additionally, the Bayesian Markov Chain Monte Carlo method was used to reconstruct a time-scaled phylogenetic tree formed by GII.P16 ORF1 sequences (n = 117) and three complete GII.P16 sequences from Belém. The phylogenetic tree indicated the presence of six clades classified into different capsid genotypes and locations. Evolutionary rates of the ORF1 gene of GII.P16 strains was estimated at 2.01 × 10^-3 substitutions/site/year, and the most recent common ancestors were estimated in 2011 (2011-2012, 95% HPD). Comparing the amino acid (AA) sequence coding for ORF1 with the prototype strain GII.P16/GII.4, 36 AA changes were observed, mainly in the non-structural proteins p48, p22, and RdRp. GII.P16/GII.4 strains of this study presented changes in amino acids 310, 333, 373, and 393 of the antigenic sites in the P2 subdomain, and ML tree indicating the division within the Sydney lineage according to the GII.P16 and GII.P31 polymerases. Notably, as noroviruses have high recombination rates and the GII.4 genotype was prevalent for a long time in several locations, additional and continuous evolutionary analyses of this new genotype should be needed in the future.