Detection in Japan of an equine-like G3P[8] reassortant rotavirus A strain that is highly homologous to European strains across all genome segments

Emergence and dissemination of equine-like G3P[8] rotavirus A in Brazil between 2015 and 2021

Rotavirus A (RVA) is a major cause of acute gastroenteritis globally that is classically genotyped by its two immunodominant outer capsid proteins, VP7 (G-) and VP4 (P-). Recent evidence suggests that the reassortant equine-like G3P[8] strain played a substantial role in RVA transmission in Brazil since 2015. To understand its global emergence and dissemination in Brazilian territory, stool samples collected from 11 Brazilian states (n = 919) were genotyped by RT-qPCR and proceeded to sequence the VP7 gene (n = 102, 79 being newly generated) of the G3P[8] samples with pronounced viral loads. Our phylogenetic genotyping showed that G3P[8] became the dominant strain in Brazil between 2017 and 2020, with equine-like variants representing 75%-100% of VP7 samples in this period. A Bayesian discrete phylogeographic analysis strongly suggests that the equine-like G3P[8] strain originated in Asia during the early 2010s and subsequently spread to Europe, the Caribbean, and South America. Multiple introductions were detected in Brazil between 2014 and 2017, resulting in five national clusters. The reconstruction of the effective population size of the largest Brazilian cluster showed an expansion until 2017, followed by a plateau phase until 2019 and subsequent contraction. Our study also supports that most mutations fixed during equine-like G3P[8] evolution were synonymous, suggesting that adaptive evolution was not an important driving force during viral dissemination in humans, potentially increasing its susceptibility to acquired immunity. This research emphasizes the need for comprehensive rotavirus genomic surveillance that allows close monitoring of its ever-shifting composition and informs more effective public health policies.IMPORTANCEOur original article demonstrated the origin and spread in a short time of equine-like G3P[8] in Brazil and the world. Due to its segmented genome, it allows numerous mechanisms including genetic drift and reassortment contribute substantially to the genetic diversity of rotavirus. Although the effectiveness and increasing implementation of vaccination have not been questioned, a matter of concern is its impact on the emergence of escape mutants or even the spread of unusual strains of zoonotic transmission that could drive epidemic patterns worldwide. This research emphasizes the need for comprehensive rotavirus genomic surveillance, which could facilitate the formulation of public policies aimed at preventing and mitigating its transmission.

Detection and full-genotype determination of rare and reassortant rotavirus A strains in Nizhny Novgorod in the European part of Russia

Reassortant DS-1-like rotavirus A strains have been shown to circulate widely in many countries around the world. In Russia, the prevalence of such strains remains unclear due to the preferred use of the traditional binary classification system. In this work, we obtained partial sequence data from all 11 genome segments and determined the full-genotype constellations of rare and reassortant rotaviruses circulating in Nizhny Novgorod in 2016-2019. DS-1-like G3P[8] and G8P[8] strains were found, reflecting the global trend. Most likely, these strains were introduced into the territory of Russia from other countries but subsequently underwent further evolutionary changes locally. G3P[8], G9P[8], and G12P[8] Wa-like strains of subgenotypic lineages that are unusual for the territory of Russia were also identified. Reassortant G2P[8], G4P[4], and G9P[4] strains with one Wa-like gene (VP4 or VP7) on a DS-1-like backbone were found, and these apparently had a local origin. Feline-like G3P[9] and G6P[9] strains were found to be phylogenetically close to BA222 isolated from a cat in Italy but carried some traces of reassortment with human strains from Russia and other countries. Thus, full-genotype determination of rotavirus A strains in Nizhny Novgorod has clarified some questions related to their origin and evolution.

Diversity of rotavirus strains circulating in Haiti before and after introduction of monovalent vaccine

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Rotaviruses are the most common cause of acute gastroenteritis among children.

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In Haiti, the most frequent genotype in the pre-vaccine period was G12P[8].

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Equine-like G3P[8] strains dominated most years following vaccine introduction.

Background

Haiti introduced a monovalent human group A rotavirus (RVA) vaccine (Rotarix) into its routine infant immunization program in April 2014. The goal of the surveillance program was to characterize RVA strains circulating in Haiti before and after RVA vaccine introduction.

Methods

Stool samples were collected from children <5 years old presenting with acute gastroenteritis at 16 hospitals in Haiti. RVA antigen enzyme immunoassay (EIA) testing was performed, and G and P genotypes were determined for positive specimens. In this study, genotype data for samples collected from May 2012 through April 2014 (the pre-vaccine introduction era) and May 2014 through July 2019 (post-vaccine introduction era) were analyzed.

Results

A total of 809 specimens were tested by the Centers for Disease Control and Prevention. During the pre-vaccine introduction era (May 2012 through April 2014), G12P[8] was the predominant genotype, detected in 88–94% of specimens. There was a high prevalence of the equine-like G3P[8] genotype among Haitian children with RVA after vaccine introduction.

Conclusions

The predominance of equine-like G3P[8] in three of five RVA seasons post-vaccine introduction suggests possible vaccine-specific selection pressure in Haiti. These temporal variations in RVA genotype predominance will require continued monitoring in Haiti as the vaccination program continues.

Temporal variations of human and animal Rotavirus A genotypes in surface water used for drinking water production

Rotavirus is a major cause of gastroenteritis among infants and children. In this study, nested PCR assays were developed to amplify partial regions of the VP7, VP4, and VP6 genes of Rotavirus A (RVA) for amplicon-based Illumina MiSeq sequencing to investigate RVA genotypes in environmental water samples. Eight sets of inner primers were first designed and screened for use in the nested PCR assays, and four sets of them could produce amplicons. Six sets of outer primers were then designed and combined with the four sets of inner primers that worked. The assays were evaluated for sensitivity using raw water samples collected from one drinking water treatment plant between April 2019 and March 2020 (Sample Set 1; N = 12) and seven DWTPs between 2018 and 2020 (Sample Set 2; N = 18). In total, 43 amplicons from Set 1 were sequenced and diverse sequences from human, porcine, bovine, equine, and feline RVA were observed. Human G8, G3, and G2 genotypes were obtained, with G8 predominant (relative abundance, 36–87%) in samples taken during the rotavirus epidemic season between April and June. Porcine G5, G11, and G4, and bovine G10 and G6 genotypes were also detected. VP4 sequence analysis revealed that the human P[8] genotype was present throughout the year, whereas P[4] and P[9] were present only in the epidemic season. The vaccine strains P[5] and P[8] (RotaTeq®) were also detected. Our approach enables the identification of prevalent human and animal RVA genotypes and their host species that potentially caused fecal contamination in water sources.

Unexpected Role of Rotavirus G3P[8] Infection in Causing Severe Diarrhea in a Major Tertiary Referral Hospital in the Prevaccine Era

Background: Rotavirus A species is associated with severe gastroenteritis in children. Rotavirus G1P[8] was the most prevalent genotype found in Kuwait in a study conducted between 2005 and 2006. The RotaTeq vaccine was included in the Kuwait national immunization program at the end of 2017. Objectives: Since there is no available data on the rotavirus genotypes circulating before the introduction of the vaccine, we conducted a study to investigate the role of rotaviruses in causing severe diarrhea in children hospitalized in a major tertiary referral hospital in Kuwait during the year 2016. Methods: Viral RNA was isolated from the stool samples of 101 children under five years of age, hospitalized for acute gastroenteritis. Rotavirus VP4 and VP7 dsRNA were detected by RT-PCR, and their partial sequences were analyzed by phylogenic analysis. Results: Rotavirus dsRNA was detected in 24.7% of children with median age of 1 year. The genotype G3P[8] accounted for 47% of cases, followed by G1P[8] (26%), G9P[8] (10.5%), G4P[8] (10.5%), and G9P[4] (5%). Only VP7 nucleotide sequences of rotavirus G3 or G4 type clustered in the same lineage as RotaTeq vaccine, while most VP4 nucleotide sequences of rotavirus P[8] type clustered in a different lineage compared to Rotarix and RotaTeq vaccines. Conclusions: Our findings highlight the role of rotavirus G3P[8] in causing severe diarrhea and invites future investigations to know whether the recent introduction of RotaTeq vaccine in Kuwait selects certain genotypes and subgenomic lineages.

Rotavirus vaccination in Japan: Efficacy and safety of vaccines, changes in genotype, and surveillance efforts

In Japan, a monovalent rotavirus vaccine (RV1) and a pentavalent rotavirus vaccine (RV5) were launched as voluntary vaccinations in November 2011 and July 2012, respectively. Rotavirus (RV) vaccine coverage in Japan increased from 30.0% in 2012 to 78.4% in 2019. The number of RV gastroenteritis hospitalizations decreased after 2014 in Japan, and is expected to decrease further following the introduction of RV vaccines into the national immunization program in October 2020. The incidence rates of intussusception (IS) among children aged <1 year were 102.8 and 94.0 per 100,000 person-years in the pre-vaccine (2007-2011) and post-vaccine (2012-September 2014) eras, respectively. IS incidence did not increase following RV vaccine introduction in Japan. The efficacy and safety of RV vaccination were both documented in Japan. To reduce the risk of IS following RV vaccination, it is important that children receive a first dose of RV vaccine at age <15 weeks, preferably at age 2 months. Some strains that have emerged since RV vaccine introduction, such as DS-1-like G1P[8], eG3, and G8P[8], have spread nationwide. These three emerging genotypes did not affect the severity of the RV infection. Continuous city-level surveillance, using analysis of all 11 RV genome segments, is necessary to elucidate the genetic characteristics of prevalent RV strains. These efforts would also clarify the influence of vaccination on genetic changes of RV strains and the emergence of new genotypes.

High prevalence of circulating DS-1-like human rotavirus A and genotype diversity in children with acute gastroenteritis in Thailand from 2016 to 2019

Background

Human rotavirus A (RVA) infection is the primary cause of acute gastroenteritis (AGE) in infants and young children worldwide, especially in children under 5 years of age and is a major public health problem causing severe diarrhea in children in Thailand. This study aimed to investigate the prevalence, genotype diversity, and molecular characterization of rotavirus infection circulating in children under 15 years of age diagnosed with AGE in Thailand from January 2016 to December 2019.

Methods

A total of 2,001 stool samples were collected from children with gastroenteritis (neonates to children <15 years of age) and tested for RVA by real-time polymerase chain reaction (RT-PCR). Amplified products were sequenced and submitted to an online genotyping tool for analysis.

Results

Overall, 301 (15.0%) stool samples were positive for RVA. RVA occurred most frequently among children aged 0-24 months. The seasonal incidence of rotavirus infection occurred typically in Thailand during the winter months (December-March). The G3P[8] genotype was identified as the most prevalent genotype (33.2%, 100/301), followed by G8P[8] (10.6%, 32/301), G9P[8] (6.3%, 19/301), G2P[4] (6.0%, 18/301), and G1P[6] (5.3%, 16/301). Uncommon G and P combinations such as G9P[4], G2P[8], G3P[4] and G3P[9] were also detected at low frequencies. In terms of genetic backbone, the unusual DS-1-like G3P[8] was the most frequently detected (28.2%, 85/301), and the phylogenetic analysis demonstrated high nucleotide identity with unusual DS-1-like G3P[8] detected in Thailand and several countries.

Conclusions

A genetic association between RVA isolates from Thailand and other countries ought to be investigated given the local and global dissemination of rotavirus as it is crucial for controlling viral gastroenteritis, and implications for the national vaccination programs.

Molecular and clinical characterization of the equine-like G3 rotavirus that caused the first outbreak in Japan, 2016

Since 2013, equine-like G3 rotavirus (eG3) strains have been detected throughout the world, including in Japan, and the strains were found to be dominant in some countries. In 2016, the first eG3 outbreak in Japan occurred in Tomakomai, Hokkaido prefecture, and the strains became dominant in other Hokkaido areas the following year. There were no significant differences in the clinical characteristics of eG3 and non-eG3 rotavirus infections. The eG3 strains detected in Hokkaido across 2 years from 2016 to 2017 had DS-1-like constellations (i.e. G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2), and the genes were highly conserved (97.5-100 %). One strain, designated as To16-12 was selected as the representative strain for these strains, and all 11 genes of this strain (To16-12) exhibited the closest identity to one foreign eG3 strain (STM050) seen in Indonesia in 2015 and two eG3 strains (IS1090 and MI1125) in another Japanese prefecture in 2016, suggesting that this strain might be introduced into Japan from Indonesia. Sequence analyses of VP7 genes from animal and human G3 strains found worldwide did not identify any with close identity (>92 %) to eG3 strains, including equine RV Erv105. Analysis of another ten genes indicated that the eG3 strain had low similarity to G2P[4] strains, which are considered traditional DS-1-like strains, but high similarity to DS-1-like G1P[8] strains, which first appeared in Asia in 2012. These data suggest that eG3 strains were recently generated in Asia as mono-reassortant strain between DS-1-like G1P[8] strains and unspecified animal G3 strains. Our results indicate that rotavirus surveillance in the postvaccine era requires whole-genome analyses.

Rotavirus A in Brazil: Molecular Epidemiology and Surveillance during 2018-2019

Rotavirus A (RVA) vaccines succeeded in lowering the burden of acute gastroenteritis (AGE) worldwide, especially preventing severe disease and mortality. In 2019, Brazil completed 13 years of RVA vaccine implementation (Rotarix™) within the National Immunization Program (NIP), and as reported elsewhere, the use of Rotarix™ in the country has reduced childhood mortality and morbidity due to AGE. Even though both marketed vaccines are widely distributed, the surveillance of RVA causing AGE and the monitoring of circulating genotypes are important tools to keep tracking the epidemiological scenario and vaccines impact. Thus, our study investigated RVA epidemiological features, viral load and G and P genotypes circulation in children and adults presenting AGE symptoms in eleven states from three out of five regions in Brazil. By using TaqMan^®-based one-step RT-qPCR, we investigated a total of 1536 stool samples collected from symptomatic inpatients, emergency department visits and outpatients from January 2018 to December 2019. G and P genotypes of RVA-positive samples were genetically characterized by multiplex RT-PCR or by nearly complete fragment sequencing. We detected RVA in 12% of samples, 10.5% in 2018 and 13.7% in 2019. A marked winter/spring seasonality was observed, especially in Southern Brazil. The most affected age group was children aged >24-60 months, with a positivity rate of 18.8% (p < 0.05). Evaluating shedding, we found a statistically lower RVA viral load in stool samples collected from children aged up to six months compared to the other age groups (p < 0.05). The genotype G3P[8] was the most prevalent during the two years (83.7% in 2018 and 65.5% in 2019), and nucleotide sequencing of some strains demonstrated that they belonged to the emergent equine-like G3P[8] genotype. The dominance of an emergent genotype causing AGE reinforces the need for continuous epidemiological surveillance to assess the impact of mass RVA immunization as well as to monitor the emergence of novel genotypes.

High prevalence of DS-1-like rotavirus infection in Thai adults between 2016 and 2019

Rotavirus infection is the most common cause of viral diarrhea in infants and young children but uncommon and usually asymptomatic in adults. In the winter of 2017–2018, a large-scale outbreak of rotavirus in both children and adults was reported in Thailand. The current study focused on the prevalence, genotyping, and molecular characterization of rotavirus infections in Thai adults from July 2016 to December 2019. In 2,598 stool samples collected from adult residents of Bangkok (aged #x2265; 15 years) with acute gastroenteritis, rotavirus was detected via real-time RT-PCR analysis of the VP6 gene. G, P and I genotypes were determined by direct sequencing of VP7, VP4, and VP6 genes, respectively. Our results showed 8.7% (226/2,598) of stool samples were positive for rotavirus. The incidence of rotavirus was high during the winter season of 2017–2018 (17.7%) compared to another studied periods (4.5% between July 2016- October 2017 and 2.8% between March 2018- December 2019). Nucleotide sequencing of VP7 and VP4 revealed G3P[8] as the predominant strain (33.2%,75/226), followed by G9P[8] (17.3%,39/226), and G2P[4] (15.0%,34/226). Uncommon G and P combinations were additionally detected at low frequencies. VP6 sequencing was conducted to discriminate I genotype between the Wa and DS-1 genogroup. The unusual DS-1-like G3P[8] strain was most prevalent amomg rotavirus strains detected in this study (29.6%, 67/226), and the corresponding VP7 sequences showed high nucleotide identity with unusual DS-1-like globally circulating strains. Our study demonstrates that rotavirus outbreaks in adults are attributable not only to high prevalence of RV infection but also the unusual DS-like genogroup. The collective findings reinforce the importance of investigating rotavirus diagnosis in adults suffering from acute gastroenteritis and taking appropriate preventive measures.

Prevalence and diversity of human rotavirus among Thai adults

Rotavirus infections have become one of the most common causes of infectious gastroenteritis in children. Although rotavirus infections have been intensively studied in infants and young children, the study in adults has been limited. As such, this study assessed the prevalence of rotaviruses and performed the molecular characterization of rotaviruses circulating in Thai adults experiencing acute gastroenteritis between January 2018 and December 2018. Group A human rotaviruses were detected in 100 feces samples by rapid immunochromatography. The peak incidence of infection occurred in February and began to decline in the summer months. From January 2018 to December 2018, there were 1344 acute gastroenteritis adult cases in the Hospital for Tropical Diseases, Bangkok, Thailand. Among these, 310 cases were rotavirus-suspected cases. Only 100 samples tested positive for rotavirus via an immunochromatography test. Twentynine out of the 100 rotavirus-positive samples were further characterized by real-time polymerase chain reaction. The G3[P8] strain was identified as the most prevalent (31.0%) followed by G1P[8], G8P[8] and G9P[8], and G2P[8], which accounted for 20.8%, 17.2%, and 13.8%, respectively. Because of the detection of rare rotavirus genotypes, such as G8, the surveillance of rotavirus epidemiology is crucial in monitoring new emergences of rotavirus strains, leading to a better understanding of the effects of strain variation for further vaccine development.

Full genome characterization of novel DS-1-like G9P[8] rotavirus strains that have emerged in Thailand

The emergence and rapid spread of unusual DS-1-like intergenogroup reassortant rotaviruses having G1/3/8 genotypes have been recently reported from major parts of the world (Africa, Asia, Australia, Europe, and the Americas). During rotavirus surveillance in Thailand, three novel intergenogroup reassortant strains possessing the G9P[8] genotype (DBM2017-016, DBM2017-203, and DBM2018-291) were identified in three stool specimens from diarrheic children. In the present study, we determined and analyzed the full genomes of these three strains. On full-genomic analysis, all three strains were found to share a unique genotype constellation comprising both genogroup 1 and 2 genes: G9-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis demonstrated that each of the 11 genes of the three strains was closely related to that of emerging DS-1-like intergenogroup reassortant, human, and/or locally circulating human strains. Thus, the three strains were suggested to be multiple reassortants that had acquired the G9-VP7 genes from co-circulating Wa-like G9P[8] rotaviruses in the genetic background of DS-1-like intergenogroup reassortant (likely equine-like G3P[8]) strains. To our knowledge, this is the first description of emerging DS-1-like intergenogroup reassortant strains having the G9P[8] genotype. Our observations will add to the growing insights into the dynamic evolution of emerging DS-1-like intergenogroup reassortant rotaviruses through reassortment.

High prevalence of equine-like G3P[8] rotavirus in children and adults with acute gastroenteritis in Thailand

Group A rotavirus (RVA) is a major cause of acute gastroenteritis in infants and young children worldwide. This study aims to clarify the distribution of G/P types and genetic characteristics of RVAs circulating in Thailand. Between January 2014 and September 2016, 1867 stool specimens were collected from children and adults with acute gastroenteritis in six provinces in Thailand. RVAs were detected in 514/1867 (27.5%) stool specimens. G1P[8] (44.7%) was the most predominant genotype, followed by G3P[8] (33.7%), G2P[4] (11.5%), G8P[8] (7.0%), and G9P[8] (1.3%). Unusual G3P[9] (0.8%), G3P[10] (0.4%), G4P[6] (0.4%), and G10P[14] (0.2%) were also detected at low frequencies. The predominant genotype, G1P[8] (64.4%), in 2014 decreased to 6.1% in 2016. In contrast, the frequency of G3P[8] markedly increased from 5.5% in 2014 to 65.3% in 2015 and 89.8% in 2016. On polyacrylamide gel electrophoresis, most (135/140; 96.4%) of the G3P[8] strains exhibited a short RNA profile. Successful determination of the nucleotide sequences of the VP7 genes of 98 G3P[8] strains with a short RNA profile showed that they are all equine-like G3P[8] strains. On phylogenetic analysis of genome segments of two representative Thai equine-like G3P[8] strains, it was noteworthy that they possessed distinct NSP4 genes, one bovine-like and the other human-like. Thus, we found that characteristic equine-like G3P[8] strains with a short RNA electropherotype are becoming highly prevalent in children and adults in Thailand.

Whole genome characterization and evolutionary analysis of OP354-like P[8] Rotavirus A strains isolated from Ghanaian children with diarrhoea

In 2010, the rare OP354-like P[8]b rotavirus subtype was detected in children less than 2 years old in Ghana. In this follow-up study, to provide insight into the evolutionary history of the genome of Ghanaian P[8]b strains RVA/Human-wt/GHA/GHDC949/2010/G9P[8] and RVA/Human-wt/GHA/GHM0094/2010/G9P[8] detected in an infant and a 7-month old child hospitalised for acute gastroenteritis, we sequenced the complete genome using both Sanger sequencing and Illumina MiSeq technology followed by phylogenetic analysis of the near-full length sequences. Both strains possessed the Wa-like/genotype 1 constellation G9P[8]b-I1-R1-C1-M1-A1-N1-T1-E1-H1. Sequence comparison and phylogenetic inference showed that both strains were identical at the lineage level throughout the 11 genome segments. Their VP7 sequences belonged to the major sub-lineage of the G9-lineage III whereas their VP4 sequences belonged to P[8]b cluster I. The VP7 and VP4 genes of the study strains were closely related to a Senegalese G9P[8]b strain detected in 2009. In the remaining nine genome segments, both strains consistently clustered together with Wa-like RVA strains possessing either P[8]a or P[8]b mostly of African RVA origin. The introduction of a P[8]b subtype VP4 gene into the stable Wa-like strain backbone may result in strains that might propagate easily in the human population, with a potential to become an important public health concern, especially because it is not certain if the monovalent rotavirus vaccine (Rotarix) used in Ghana will be efficacious against such strains. Our analysis of the full genomes of GHM0094 and GHDC949 adds to knowledge of the genetic make-up and evolutionary dynamics of P[8]b rotavirus strains.

Sub-genotype phylogeny of the non-G, non-P genes of genotype 2 Rotavirus A strains

Recent increase in the detection of unusual G1P[8], G3P[8], G8P[8], and G9P[4] Rotavirus A (RVA) strains bearing the DS-1-like constellation of the non-G, non-P genes (hereafter referred to as the genotype 2 backbone) requires better understanding of their evolutionary relationship. However, within a genotype, there is lack of a consensus lineage designation framework and a set of common sequences that can serve as references. Phylogenetic analyses were carried out on over 8,500 RVA genotype 2 genes systematically retrieved from the rotavirus database within the NCBI Virus Variation Resource. In line with previous designations, using pairwise comparison of cogent nucleotide sequences and stringent bootstrap support, reference lineages were defined. This study proposes a lineage framework and provides a dataset ranging from 34 to 145 sequences for each genotype 2 gene for orderly lineage designation of global genotype 2 genes of RVAs detected in human and animals. The framework identified five to 31 lineages depending on the gene. The least number of lineages (five to seven) were observed in genotypes A2 (NSP1), T2 (NSP3) and H2 (NSP5) which are limited to human RVA whereas the most number of lineages (31) was observed in genotype E2 (NSP4). Sharing of the same lineage constellations of the genotype 2 backbone genes between recently-emerging, unusual G1P[8], G3P[8], G8P[8] and G9P[4] reassortants and many contemporary G2P[4] strains provided strong support to the hypothesis that unusual genotype 2 strains originated primarily from reassortment events in the recent past involving contemporary G2P[4] strains as one parent and ordinary genotype 1 strains or animal RVA strains as the other. The lineage framework with selected reference sequences will help researchers to identify the lineage to which a given genotype 2 strain belongs, and trace the evolutionary history of common and unusual genotype 2 strains in circulation.

Whole genome characterization of feline-like G3P[8] reassortant rotavirus A strains bearing the DS-1-like backbone genes detected in Vietnam, 2016

While conducting rotavirus gastroenteritis surveillance in Vietnam, two G3P[8] rotavirus A specimens possessing an identical short RNA electropherotype were detected. They were RVA/Human-wt/VNM/0232/2016/G3P[8] and RVA/Human-wt/VNM/0248/2016/G3P[8], and recovered from 9 and 23 months old boys, respectively. The patients developed diarrhoea within one-week interval in March 2016 but in places >100 km apart in northern Vietnam. Whole genome sequencing of the two G3P[8] rotavirus A strains revealed that their genomic RNA sequences were identical across the 11 genome segments, suggesting that they derived from a single clone. The backbone gene constellation was I2-R2-C2-M2-A2-N2-T2-E2-H2. The backbone genes and the VP4 gene had a virtually identical nucleotide sequences with identities ranging from 99.2 to 100% to the corresponding genes of RVA/Human-wt/VNM/1149/2014/G8P[8]; the prototype of recently-emerging bovine-like G8P[8] reassortant strains in Vietnam. On the other hand, the VP7 gene was 98.8% identical with that of RVA/Human-wt/CHN/E2451/2011/G3P[9], and they were clustered together in the lineage represented by RVA/Cat-tc/JPN/FRV-1/1986/G3P[9]. The observations led us to hypothesise that one of the bovine-like G8P[8] strains bearing the DS-1-like backbone genes reassorted with a locally circulating FRV-1-like strain to gain the G3 VP7 gene and to emerge as a thus-far undescribed feline-like G3P[8] reassortant strain. The identification of feline-like G3P[8] strains bearing the DS-1-like backbone genes exemplifies the strength and necessity of the whole genome sequencing approach in monitoring, describing and understanding the evolutionary changes that are occurring in emerging strains and their interactions with co-circulating strains.

Genetic characterization of a novel G9P[23] rotavirus A strain identified in southwestern China with evidence of a reassortment event between human and porcine strains

Group A rotaviruses (RVAs) are important zoonotic pathogens that cause intestinal disease in humans and other mammals. In this study, the novel strain RVA/Pig/China/SC11/2017/G9P[23](SC11) was isolated from fecal samples from a pig farm in Sichuan province, southwestern China. The complete genome was found to be 18,347 bp in length with 11 segments. The genotype constellation of strain SC11 was G9-P[23]-I12-R1-C1-M1-A1-N1-T1-E1-H1, according to whole-genome sequencing analysis. The VP1, VP2, VP4, VP6, NSP1-NSP3, and NSP5 genes of RVA strain SC11 were found to be closely related to those of porcine and/or porcine-like human RVAs. Meanwhile, the VP7 and NSP4 genes of strain SC11 were closely related to genes of human RVAs. However, it was difficult to pinpoint the porcine or human origin of the VP3 gene of strain SC11 based on the available data. These results showed that SC11 originated from a natural reassortment event between human and pig RVA strains, and crossover points for recombination were identified at nucleotides (nt) 109-806 of NSP2. This is the first report of such a reassortant and recombinant RVA strain in the southwestern region of China.

Genomic characterization of uncommon human G3P[6] rotavirus strains that have emerged in Kenya after rotavirus vaccine introduction, and pre-vaccine human G8P[4] rotavirus strains

A monovalent rotavirus vaccine (RV1) was introduced to the national immunization program in Kenya in July 2014. There was increased detection of uncommon G3P[6] strains that coincided temporally with the timing of this vaccine introduction. Here, we sequenced and characterized the full genomes of two post-vaccine G3P[6] strains, RVA/Human-wt/KEN/KDH1951/2014/G3P[6] and RVA/Human-wt/KEN/KDH1968/2014/G3P[6], as representatives of these uncommon strains. On full-genomic analysis, both strains exhibited a DS-1-like genotype constellation: G3-P[6]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis revealed that all 11 genes of strains KDH1951 and KDH1968 were very closely related to those of human G3P[6] strains isolated in Uganda in 2012-2013, indicating the derivation of these G3P[6] strains from a common ancestor. Because the uncommon G3P[6] strains that emerged in Kenya are fully heterotypic as to the introduced vaccine strain regarding the genotype constellation, vaccine effectiveness against these G3P[6] strains needs to be closely monitored.

Spread of the emerging equine-like G3P[8] DS-1-like genetic backbone rotavirus strain in Brazil and identification of potential genetic variants

In 2013, the equine-like G3P[8] DS-1-like rotavirus (RVA) strain emerged worldwide. In 2016, this strain was reported in northern Brazil. The aims of the study were to conduct a retrospective genetic investigation to identify the possible entry of these atypical strains in Brazil and to describe their distribution across a representative area of the country. From 2013 to 2017, a total of 4226 faecal samples were screened for RVA by ELISA, PAGE, RT-PCR and sequencing. G3P[8] represented 20.9 % (167/800) of all RVA-positive samples, further subdivided as equine-like G3P[8], DS-1-like (11.0 %; 88/800) and Wa-like G3P[8] (9.9 %; 79/800). Six equine-like G3P[8] DS-1-like samples were selected for whole-genome investigation, confirming the backbone I2-R2-C2-M2-A2-N2-T2-E2-H2. During 2013-2014, Wa-like G3P[8] was predominant and no equine-like G3P[8] DS-1-like was detected. Equine-like G3P[8] DS-1-like was first identified in Paraná in March/2015, suggesting that the strain entered Brazil through the Southern region. Equine-like G3P[8] rapidly spread across the area under surveillance and displayed a marked potential to replace Wa-like G3P[8] strains. Brazilian equine-like G3P[8] DS-1-like strains clustered with contemporary equine-like G3P[8] DS-1-like detected worldwide, but exhibited a distinct NSP2 genotype (N2) compared to the previously reported Amazon equine-like G3P[8] DS-1-like strain (N1). Two distinct NSP4 E2 genotype lineages were also identified. Taken together, these data suggest that different variants of equine-like G3P[8] DS-1-like strains might have been introduced into the country at distinct time points, and co-circulated in the period 2015-2017. The global emergence of equine-like G3P[8] DS-1-like strains, predominantly in countries using the Rotarix vaccine, raises the question of whether vaccines may be inducing selective pressures on zoonotic strains.