Molecular Evolution of GII.P31/GII.4_Sydney_2012 Norovirus over a Decade in a Clinic in Japan.

Norovirus (NoV) genogroup II, polymerase type P31, capsid genotype 4, Sydney_2012 variant (GII.P31/GII.4_Sydney_2012) has been circulating at high levels for over a decade, raising the question of whether this strain is undergoing molecular alterations without demonstrating a substantial phylogenetic difference. Here, we applied next-generation sequencing to learn more about the genetic diversity of 14 GII.P31/GII.4_Sydney_2012 strains that caused epidemics in a specific region of Japan, with 12 from Kyoto and 2 from Shizuoka, between 2012 and 2022, with an emphasis on amino acid (aa) differences in all three ORFs. We found numerous notable aa alterations in antigenic locations in the capsid region (ORF2) as well as in other ORFs. In all three ORFs, earlier strains (2013-2016) remained phylogenetically distinct from later strains (2019-2022). This research is expected to shed light on the evolutionary properties of dominating GII.P31/GII.4_Sydney_2012 strains, which could provide useful information for viral diarrhea prevention and treatment.

Sapovirus infections in Japan before and after the emergence of the COVID-19 pandemic: An alarming update.

An increasing trend of sapovirus (SaV) infections in Japanese children during 2009-2019, particularly after the introduction of the voluntary rotavirus (RV)-vaccination program has been observed. Herein, we investigated the epidemiological situation of SaV infections from 2019 to 2022 when people adopted a precautionary lifestyle due to the emergence of the COVID-19 pandemic, and RV vaccines had been implemented as routine vaccines. Stool samples were collected from children who attended outpatient clinics with acute gastroenteritis and analyzed by reverse transcriptase-polymerase chain reaction to determine viral etiology. Among 961 stool samples, 80 (8.3%) were positive for SaV: 2019-2020 (6.5%), 2020-2021 (0%), and 2021-2022 (12.8%). The trend of SaV infection in Japanese children yet remained upward with statistical significance (p = 0.000). The major genotype was GI.1 (75%) which caused a large outbreak in Kyoto between December 2021 and February 2022. Phylogenetic, gene sequence and deduced amino acid sequence analyses suggested that these GI.1 strains detected in the outbreak and other places during 2021-2022 or 2019-2020 remained genetically identical and widely spread. This study reveals that SaV infection is increasing among Japanese children which is a grave concern and demands immediate attention to be paid before SaV attains a serious public health problem.

Genetic diversity and declining norovirus prevalence in infants and children during Japan's COVID-19 pandemic: a three-year molecular surveillance.

Noroviruses (NoVs) are a global concern, causing widespread outbreaks and sporadic acute gastroenteritis (AGE) cases across all age groups. Recent research has shed light on the emergence of novel recombinant strains of NoV in various countries. To delve deeper into this phenomenon, we extensively analyzed 1,175 stool samples collected from Japanese infants and children with AGE from six different prefectures in Japan over three years, from July 2018 to June 2021. Our investigation aimed to determine the prevalence and genetic characteristics of NoV associated with sporadic AGE while exploring the possibility of detecting NoV recombination events. Among the analyzed samples, we identified 355 cases positive for NoV, 11 cases attributed to GI genotypes, and 344 associated with GII genotypes. Notably, we discovered four distinct GI genotypes (GI.2, GI.3, GI.4, and GI.6) and seven diverse GII genotypes (GII.2, GII.3, GII.4, GII.6, GII.7, GII.14, and GII.17). The predominant genotypes were GII.4 (56.4%; 194 out of 344), followed by GII.2 and GII.3. Through dual genotyping based on sequencing of the ORF1/ORF2 junction region, we identified a total of 14 different RdRp/capsid genotypes. Of particular interest were the prevalent recombinant genotypes GII.4[P31] and GII.2[P16]. Notably, our study revealed a decrease in the number of children infected with NoV during and after the COVID-19 pandemic. These findings underscore the importance of continuous NoV surveillance efforts.

The Detection of Rotavirus Antigenemia by Immunochromatographic Kits: a Case Series.

BACKGROUND: Acute gastroenteritis is the most common cause of illness and death in infants and young children worldwide. Rotaviruses (RVs) are the major viruses that cause acute gastroenteritis in young children, especially in developing countries in Asia and Africa. METHODS: The presence of rotavirus antigens in sera of four unvaccinated pediatric patients, aged between 4 and 6 years with severe diarrhea and dehydration, were detected by using three immunochromatographic (IC) kits. In addition, the presence of anti-rotavirus IgG, IgA, and IgM antibodies and their concentrations in patient sera were also determined by enzyme immunoassay (EIA). RESULTS: All three kits could detect rotavirus antigen in patient sera with different intensity of the test lines. When patient sera were pretreated with anti-VP6 rotavirus mouse monoclonal antibody prior to testing, the rotavirus positive test lines disappeared, suggesting that all patient sera contained VP6 protein antigen of rotavirus. Assessment of antibody concentration in these patient sera revealed that all patient sera contained IgG, IgA, and IgM antibodies against rotavirus antigen at different concentrations. CONCLUSIONS: The sensitivity of rotavirus protein detection in the patient sera of one IC kit brand was comparable to those of the EIA, suggesting this IC kit could be an alternative screening method for rapid diagnosis of rotavirus infection.

Molecular analysis of amantadine-resistant influenza A (H1N1 pdm09) virus isolated from slum dwellers of Dhaka, Bangladesh.

Influenza is a highly contagious viral infection associated with excessive hospitalizations and deaths throughout the world. Continuous antigenic shift and drift is not only responsible for this devastating effect of influenza but also causes ineffectiveness of antiviral drugs and vaccines. In this study, we investigated the effectiveness of ribavirin, oseltamivir, and amantadine drugs in vitro against nine influenza A isolates collected during June 2012-August 2013 from different slums in Dhaka city. The effectiveness of these drugs was determined by measuring the inhibition of virus-induced cytopathic effect on MDCK cells through MTT assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). Our data showed that all nine influenza isolates (6 H1N1 pdm09 and 3 H3N2 subtypes) were completely susceptible to ribavirin (The 50% effective concentrations, EC50 3.0 µg/ml) and oseltamivir (EC50 0.35 µg/ml). When influenza A infection was challenged with amantadine drug, eight out of nine isolates (88%) demonstrated susceptibility to amantadine drug (EC50 0.30 µg/ml) while one H1N1 pdm09 isolate exhibited higher EC50 value (>10 µg/ml) beyond the cell tolerance level of drug (>5 µg/ml). Genetic analysis of transmembrane matrix protein 2 (M2), which is a target for the amantadine drug and vital for viral replication, showed a substitution of amino acid at position 31(S31 N) of that amantadine-resistant isolate indicating the possible reason of amantadine drug resistance.

Evaluation of a novel triplex immunochromatographic test for rapid simultaneous detection of norovirus, rotavirus, and adenovirus on a single strip test.

BACKGROUND: Acute gastroenteritis is one of the major causes of morbidity and mortality in young children worldwide. Among these, rotavirus, norovirus, and adenovirus have been reported as the primary viral pathogens associated with the disease. Rapid diagnosis of viral pathogens is crucial when diarrhea outbreaks occur to ensure the timely administration of appropriate treatment and control measures. METHODS: We evaluated three immunochromatographic test kits designed for the detection of norovirus, rotavirus, and adenovirus in 71 stool specimens collected from children with diarrhea who visited clinics in Japan. The first kit is a triplex immunochromatographic test kit designed for simultaneous detections of norovirus, rotavirus, and adenovirus on a single strip (this kit was referred to as IC-A). The other two immunochromatographic test kits are a dual detection kit for rotavirus and adenovirus, and a single detection kit for norovirus (IC-B). The RT-PCR/PCR was used as the gold standard method. RESULTS: The results revealed that both IC-A and IC-B kits exhibited the same level of sensitivity of detection for rotavirus (72.7%) and adenovirus (22.7%), although the detection rate was lower than that of the RT-PCR/PCR method. However, there was a slight difference in the sensitivity of detection for norovirus between IC-A and IC-B, at 86.7% and 93.3%, respectively. The sensitivity of detection for adenovirus of both kits was relatively lower than those of RT-PCR method. This could be due to low viral load of adenovirus in clinical specimens below the detection limit of IC-A and IC-B kits. However, both immunochromatographic test kits (IC-A and IC-B) exhibited 100% specificity for norovirus, rotavirus, and adenovirus. CONCLUSIONS: The triplex immunochromatographic test kit (IC-A) designed for simultaneous detection of norovirus, rotavirus, and adenovirus has been proved to be more practical and convenient than the use of single or dual detection kits with more or less the same sensitivity and specificity of detections.

Transient heating of expressed breast milk up to 65°C inactivates HIV-1 in milk: a simple, rapid, and cost-effective method to prevent postnatal transmission.

The postnatal transmission of human immunodeficiency virus (HIV) from mothers to children occurs through breastfeeding. Although heat treatment of expressed breast milk is a promising approach to make breastfeeding safer, it is still not popular, mainly because the recommended procedures are difficult to follow, or time-consuming, or because mothers do not know which temperature is sufficient to inactivate HIV without destroying the nutritional elements of milk. To overcome these drawbacks, a simple and rapid method of heat treatment that a mother could perform with regular household materials applying her day-to-day art of cooking was examined. This structured experiment has demonstrated that both cell-free and cell-associated HIV type 1 (HIV-1) in expressed breast milk could be inactivated once the temperature of milk reached 65°C. Furthermore, a heating method as simple as heating the milk in a pan over a stove to 65°C inhibited HIV-1 transmission retaining milk's nutritional key elements, for example, total protein, IgG, IgA, and vitamin B(12) . This study has highlighted a simple, handy, and cost-effective method of heat treatment of expressed breast milk that mothers infected with HIV could apply easily and with more confidence.

X4-tropic human immunodeficiency virus IIIB utilizes CXCR4 as coreceptor, as distinct from R5X4-tropic viruses.

Human immunodeficiency viruses initiate infections via CCR5 coreceptors and then change their tropism to C-X-C chemokine receptor type 4 (CXCR4), this change being associated with rapid disease progression. HIV-1IIIB, a widely described pure X4-tropic strain, is distinct from R5X4-tropic viruses. In this study, the requirement for amino terminal regions (NTRs) of CXCR4 for entry of HIV-1IIIB virus into host cells was examined and compared to that of R5X4-tropic viruses. CXCR4 and its deletion mutant (CXCR4ΔNTR23; first 23 amino acids removed from NTR) were amplified to examine their coreceptor activities. NP-2/CD4/CXCR4 and NP-2/CD4/CXCR4ΔNTR23 cell lines were prepared accordingly. Indirect immune fluorescence assay (IFA), PCR, and reverse transcriptase (RT) activity were used to compare the process of infection of host cells by HIV-1IIIB virus, one R5-tropic and five other R5X4-tropic viruses. All the R5X4-tropic HIVs were found to utilize both CCR5 and CXCR4 but unable to use CXCR4ΔNTR23 as coreceptors. In contrast, X4-tropic HIV-1IIIB was found to preferentially infect through CXCR4ΔNTR23. Viral antigens in infected NP-2/CD4/CXCR4ΔNTR23 cells were detected by IFA and confirmed by detection of proviral DNA and by performing RT assays on the spent cell-supernatants. In dual tropic viruses, deletion of 23 amino acids from NTR abrogates the coreceptor activity of CXCR4. This observation demonstrates that NTR of CXCR4 have an obligatory coreceptor role for dual tropic viruses. However, HIV-1IIIB may have different requirements for NTR than R5X4 viruses or may infect host cells independent of NTR of CXCR4.

Outbreak of human astroviruses 1 and Melbourne 2 in acute gastroenteritis pediatric patients in Japan during the COVID-19 pandemic, 2021.

BACKGROUND: Human astrovirus (HAstV) infection is one of the leading causes of acute gastroenteritis in young children. The present study reports the outbreak of HAstV in children with acute gastroenteritis in Kyoto, Japan, during the COVID-19 pandemic, 2021. METHODS: A total of 61 stool samples were collected from children with acute gastroenteritis who visited a pediatric outpatient clinic in Maizuru city, Kyoto, Japan from July to October, 2021. HAstV was screened by RT-PCR, and the genotypes were identified by nucleotide sequence analysis. RESULTS: Of 61 cases of acute gastroenteritis, 20 were mono-infected with HAstV alone. In addition, mixed infection of HAstV and NoV, and HAstV and RVA were also detected in 15 and 1 cases, respectively. Of 36 HAstV strains detected in this outbreak, 29 and 7 were HAstV1 and MLB2 genotypes, respectively. All HAstV1 strains were closely related to the HAstV1 reported from Thailand and Japan in 2021 and all of them belonged to subgenotype HAstV1a. Among MLB2, they were most closely related to the MLB2 strains reported from China in 2016 and 2018. CONCLUSIONS: After the kindergartens and schools were re-opened at the middle of 2021 in Japan, an outbreak of HAstV was reported. Control measures against the COVID-19 pandemics might affect the spread of diarrheal virus infection. Here we report the outbreak of HAstV1 and MLB2 in Kyoto, Japan, during COVID-19 pandemic in 2021.

Genotype Diversity of Enteric Viruses in Wastewater Amid the COVID-19 Pandemic.

Viruses remain the leading cause of acute gastroenteritis (AGE) worldwide. Recently, we reported the abundance of AGE viruses in raw sewage water (SW) during the COVID-19 pandemic, when viral AGE patients decreased dramatically in clinics. Since clinical samples were not reflecting the actual state, it remained important to determine the circulating strains in the SW for preparedness against impending outbreaks. Raw SW was collected from a sewage treatment plant in Japan from August 2018 to March 2022, concentrated by polyethylene-glycol-precipitation method, and investigated for major gastroenteritis viruses by RT-PCR. Genotypes and evolutionary relationships were evaluated through sequence-based analyses. Major AGE viruses like rotavirus A (RVA), norovirus (NoV) GI and GII, and astrovirus (AstV) increased sharply (10-20%) in SW during the COVID-19 pandemic, though some AGE viruses like sapovirus (SV), adenovirus (AdV), and enterovirus (EV) decreased slightly (3-10%). The prevalence remained top in the winter. Importantly, several strains, including G1 and G3 of RVA, GI.1 and GII.2 of NoV, GI.1 of SV, MLB1 of AstV, and F41 of AdV, either emerged or increased amid the pandemic, suggesting that the normal phenomenon of genotype changing remained active over this time. This study crucially presents the molecular characteristics of circulating AGE viruses, explaining the importance of SW investigation during the pandemic when a clinical investigation may not produce the complete scenario.

The Emergence and Widespread Circulation of Enteric Viruses Throughout the COVID-19 Pandemic: A Wastewater-Based Evidence.

Growing evidence shed light on the importance of wastewater-based epidemiology (WBE) during the pandemic, when the patients rarely visited the clinics despite the fact that the infections were still prevalent in the community as before. The abundance of infections in the community poses a constant threat of the emergence of new epidemic strains. Herein, we investigated enteric viruses in raw sewage water (SW) from Japan's Tohoku region and compared them to those from the Kansai region to better understand the circulating strains and their distribution across communities during the COVID-19 pandemic. Raw SW was collected between 2019 and 2022, concentrated by polyethylene-glycol-precipitation method, and investigated for major AGE viruses by RT-PCR. Sequence-based analyses were used to assess genotypes and evolutionary relationships. The most commonly detected enteric virus was rotavirus A (RVA) at 63.8%, followed by astrovirus (AstV) at 61.1%, norovirus (NoV) GII and adenovirus (AdV) at 33.3%, sapovirus (SV) at 25.0%, enterovirus (EV) at 19.4%, and NoV GI at 13.9%. The highest prevalence (46.0%) was found in the spring. Importantly, enteric viruses did not decline during the pandemic. Rather, several strains like NoV GII.2, DS-1-like human G3 (equine) RVA, MLB1 AstV, and different F41 HAdV emerged throughout the pandemic and spread widely over the Tohoku and Kansai regions. Tohoku's detection rate remained lower than that of the Kansai area (36 vs 58%). This study provides evidence for the emergence and spread of enteric viruses during the pandemic.

Ionising irradiation alters the dynamics of human long interspersed nuclear elements 1 (LINE1) retrotransposon.

It is important to identify the mechanism by which ionising irradiation induces various genomic alterations in the progeny of surviving cells. Ionising irradiation activates mobile elements like retrotransposons, although the mechanism of its phenomena consisting of transcriptions and insertions of the products into new sites of the genome remains unclear. In this study, we analysed the effects of sparsely ionising X-rays and densely ionising carbon-ion beams on the activities of a family of active retrotransposons, long interspersed nuclear elements 1 (L1). We used the L1/reporter knock-in human glioma cell line, NP-2/L1RP-enhanced GFP (EGFP), that harbours full-length L1 tagged with EGFP retrotransposition detection cassette (L1RP-EGFP) in the chromosomal DNA. X-rays and carbon-ion beams similarly increased frequencies the transcription from L1RP-EGFP and its retrotransposition. Short-sized de novo L1RP-EGFP insertions with 5'-truncation were induced by X-rays, while full-length or long-sized insertions (>5 kb, containing ORF1 and ORF2) were found only in cell clones irradiated by the carbon-ion beams. These data suggest that X-rays and carbon-ion beams induce different length of de novo L1 insertions, respectively. Our findings thus highlight the necessity to investigate the mechanisms of mutations caused by transposable elements by ionising irradiation.

Changing distribution of rotavirus A genotypes circulating in Japanese children with acute gastroenteritis in outpatient clinic, 2014-2020.

BACKGROUND: Rotavirus A (RVA) is a major cause of severe acute gastroenteritis (AGE) in infants and children worldwide. In Japan, two kinds of rotavirus vaccines have been introduced as voluntary vaccines in 2011 and 2012, respectively, and launched into the national vaccine program in October 2020. METHODS: In this study, we investigated prevalence of RVA and their molecular characterization in the stool samples collected from infants and children with AGE who visited one outpatient clinic in Japan, from July 2014 to June 2020, during voluntary vaccination with two kinds of rotavirus vaccines. RESULTS: The RVA detection rates decreased from 44.7 % in 2014-2015 to 35.4 % in 2018-2019, whereas in 2019-2020 the numbers of samples collected were dramatically decreased and none of RVA was detected. During this study period, rotavirus vaccination rates in this area increased from 32.4 % to 62.2 %. Distribution of RVA VP7 (G), VP4 (P), and VP6 (I) genotypes in this area had changed year by year; the major genotype combinations were G1P[8]I1 and G1P[8]I2 in 2014-2015, G2P[4]I2 and G9P[8]I1 in 2015-2016, G1P[8]I1 and G8P[8]I2 in 2017-2018, and G8P[8]I2 in 2018-2019. Phylogenetic analysis demonstrated that VP7 nucleotide sequences of G1 were genetically diverse compared with those of other G genotypes in this study. Meanwhile, predominance of unusual G2P[8]I1, G2P[8]I2 and mixed P genotypes were observed only in 2016-2017, but did not carry on in 2017-2019. The equine-like G3 was detected only in 2016-2017. CONCLUSIONS: The results revealed diversity of RVA genotypes and the genotype combinations have changed year by year in Japan, during the study period of 2016-2020.

Detection of Rotavirus Strains in Freshwater Clams in Japan.

Bivalve molluscan shellfish like clams and oysters, etc., are capable to bioaccumulate surrounding contaminants from waters into their digestive systems and posing serious threats of food poisoning. Detection of rotaviruses (RVs) in shellfish is of particular importance because RVs are prone to genome reassortment resulting in the emergence of new RV variants that may compromise vaccine safety. Herein, we have detected the wild-type RVs and Rotarix/RotaTeq vaccine strains in freshwater clams collected on the riverside, Kawasaki city, from July 2019 to January 2020 and correlated the detected genotypes with that of gastroenteritis cases of nearby clinics to understand the transmission of RVs in the environment. The wild-type RVs were detected in 62 (64.6%) out of 96 freshwater clams in every study month: July, September, November, and January that are considered as off-season for RV infections. The most frequent genotypes were G2 (42.9%), G8 (28.6%), G3 (14.3%), G1 (7.1%), and G10 (7.1%), which remained comparable with genotypic distribution found in the clinical samples over the last few years indicating that these RVs may accumulate in clams since a long time. However, G10 genotype was detected in clam but not in clinical samples suggesting the presence of asymptomatic infection or RVs could be carried out from a long distance. Importantly, vaccine strains, RotaTeq (1%) but not Rotarix (0%), were also detected in a clam. Attention must be paid to monitoring the potential transmission of wild-type and vaccine RV strains in the environment to prevent the emergence of new variants generated from genome reassortment with vaccine strains.

An increasing trend of human sapovirus infection in Japan, 2009 to 2019: An emerging public health concern.

BACKGROUND: Human sapovirus (SaV) is an important etiologic agent of childhood diarrhea. This study aims to investigate the burden of SaV infection in childhood diarrhea in Japan from 2009-2019, to understand the changes in SaV infection after the introduction of rotavirus (RV) vaccination in Japan in 2011. METHODS: Stool samples were collected from children aged ≤ 12 years old with acute gastroenteritis (AGE) who visited outpatient clinics of six prefectures in Japan. The viral RNA was detected by RT-PCR and genogroups and genotypes were determined through sequence-based analysis. RESULTS: Among 5697 stool samples, 318 (5.6%) samples remained SaV-positives showing the highest prevalence in June and 12-24 month aged children. The most predominant genotype was GI.1 (56.8%), followed by GI.2 (19.2%), GII.1 (10.8%), GIV.1 (9.4%), GI.3 (1.7%), GII.2 (1.4%), GII.3 and GII.5 (0.3%). Importantly, an increasing trend (P = 0.016) of SaV infection was observed during this period. In particular, SaV-detection rate was increased significantly (P = 0.033) from 4.3% in pre-rotavirus (RV)-vaccination era to 6.1% in post-RV-vaccination era. We provided evidence that this increase in SaV infection was mainly attributed by coinfections. CONCLUSIONS: The upward trend of SaV infection, particularly after the introduction of RV-vaccination, is an emerging concern. Attention should be paid to control this upward trend of SaV infection to ensure maximum benefits of implementation of RV vaccines towards reducing overall childhood diarrhea worldwide.

Genetic diversity of Parechovirus A in infants and children with acute gastroenteritis in Japan during 2016-2018.

Parechovirus A (PeV-A), previously known as human parechovirus, is a common pathogen in children that can cause respiratory and gastrointestinal diseases as well as severe neurological disease. Take advantage of our previous findings on the genetic diversity of PeV-A circulating in Japanese children with acute gastroenteritis (AGE), this study was conducted to investigate the genetic diversity of PeV-A isolated from children with AGE in Japan as well as their clinical symptoms. Of 1070 stool samples collected from Japanese infants and children with AGE during the 2-year period from July 2016 to June 2018, 76 were positive for PeV-A by multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) and were subjected to genotyping based on viral protein 1 (VP1) sequences. Five different PeV-A genotypes including PeV-A1B, -A2, -A3, -A4, and -A6 were detected with predominant of PeV-A1 clade B genotype. This study revealed a high genetic diversity of PeV-A circulating in Japanese infants and children with AGE and the PeV-A2, a rare genotype, was detected for the first time in Japan in patients with AGE. The clinical symptoms observed in these patients included diarrhea, vomiting, fever, cough, rhinorrhea, and dehydration.

Role of rotavirus vaccination on G9P[8] rotavirus strain during a seasonal outbreak in Japan.

Although two live oral rotavirus (RV) vaccines, Rotarix and RotaTeq, play a critical role toward reducing disease severity, hospitalization, and death rate in RV infections, regular monitoring of vaccine effectiveness (VE) is yet necessary because the segmented genome structure and reassortment capability of RVs pose considerable threats toward waning VE. In this study, we examined the VE by a test-negative study design against G9P[8]I2 strain during a seasonal outbreak in February-May, 2018, in an outpatient clinic in Kyoto Prefecture, Japan. It remains important because G9P[8]I2 strain remains partially heterotypic to these vaccines and predominating in post-vaccination era. During year-long surveillance, RV infections were detected only from February to May. During this outbreak, 33 (42.3%) children out of 78 with acute gastroenteritis (AGE) remained RV-positive, of which 29 (87.8%) children were infected with G9P[8]I2. Two immunochromatographic (IC) assay kits exhibited 100% sensitivity and specificity to detect G9P[8]I2 strain. Only 23.2% children were found to be vaccinated. Yet, significant VE 69.7% (95% CI: 2.5%-90.6%) was recognized against all RV strains that increased with disease severity. Similar significant VE 71.8% (95% CI: 1%-92%) was determined against G9P[8]I2 strain. The severity score remained substantially low in vaccinated children. Our data reveal that vaccine-preventable G9P[8]I2 strain yet may cause outbreak where vaccination coverage remains low. Thus, this study emphasizes the necessity of global introduction of RV-vaccines in national immunization programs of every country.

Diagnosis of Acute Gastroenteritis with Immunochromatography and Effectiveness of Rotavirus Vaccine in a Japanese Clinic.

Despite the well known effectiveness of two licensed live attenuated oral rotavirus (RV)-vaccines, Rotarix and RotaTeq, constant monitoring of vaccine effectiveness (VE) is essential considering the evolving power and reassortment capability of RVs. In this study, we detected RV, norovirus (NV) and adenovirus (AV) infections using immunochromatography (IC)-based kits in children with acute gastroenteritis (AGE) who attended a pediatric clinic in Kiryu city, Gunma, Japan during June, 2014-September, 2018. VEs were determined using a test-negative study design. Among 1658 AGE-children, RV, NV and AV were detected in 96 (5.8 %), 146 (8.8 %) and 46 (2.8 %) children, respectively. Interestingly, the distributions of infections were found to be associated with age and sex. Namely, RV infections were significantly higher in female (P=0.02) and in the 19-30 month age group children, while NV and AV infections predominated in the 13-24 month and 7-18 month age groups, respectively. The disease severity for RV and NV infections remained similar and significantly higher than that of AV infections. The VE of RV-vaccines was 49.8 % (95 % CI: 22.7 to 67.3 %) against all RV infections, which was increased up to 67.2 % (95 % CI: 35.3 to 83.4 %) against severe RV infections. RV-vaccinated children experienced less severe symptoms in RV-infections while non-RV AGE remained less serious for both RV-vaccinated and unvaccinated children. Finally, the prevalence of RV infection remained minimized (≤5.4 %) in this population since 2015. Thus, this study provided important information on distribution of major AGEs in young children and exhibited the effective role of RV vaccines in post-vaccine era.

Distribution of rotavirus genotypes in Japan from 2015 to 2018: Diversity in genotypes before and after introduction of rotavirus vaccines.

BACKGROUND: Diversity in group A rotavirus (RVA) strains after introduction of RV-vaccines remains an emerging concern worldwide. In this study, we investigated the prevalence and distribution of RVA genotypes in Japanese children with acute gastroenteritis (AGE) from 2015 to 2018. In addition, a comparison of the genotypes in pre-vaccination (2006-2012) and post-vaccination (2012-2018) periods was conducted to understand the impact of these vaccines on genotype distribution. METHODS: Fecal samples were collected regularly from outpatient clinics in six localities: Hokkaido, Tokyo, Shizuoka, Osaka, Kyoto, and Saga. RVA were screened and genotyped by RT-PCR and sequence-based genotyping. RESULTS: During the period 2015-2018, RVA was detected in 307 (19.7%) samples out of 1557 specimens: 29.9% (95% CI: 25.8% to 34.3%), 17.9% (95% CI: 14.7% to 21.5%), and 13% (95% CI: 10.3% to 16.0%) were detected RVA-positive in 2015-2016, 2016-2017 and 2017-2018, respectively. The average detection of RVA in pre-vaccination (2006-2012) and post-vaccination (2012-2018) era remained almost similar (18%-20%). The G2P[4]I2 (52.1%, 95% CI: 43.5%-60.6%) remained the most common genotype in 2015-2016, whereas G8P[8]I2 (55.9%, 95% CI: 45.2%-66.2%) dominated in 2016-2017. In 2017-2018, G9P[8]I2 (42.0%, 95% CI: 30.5%-53.9%) prevailed, followed by G9P[8]I1 (23.0%, 95% CI: 14.0%-34.2%). The detection rate of some common genotypes of pre-vaccination era like G1P[8] and G3P[8] has been reduced after introduction of RV-vaccine, whereas genotypes that were sporadic before the introduction of vaccines like G2P[4], G2P[8], G9P[8] and G8P[8] were emerged/reemerged in post-vaccination period. CONCLUSIONS: Our study presented the diversity in circulating RVA genotypes in Japan before and after introduction of RV-vaccines. Sudden emergence of DS-1-like (I2) unusual strains in post-vaccination era remains alarming. Continuous monitoring of RVA genotypes is therefore indispensable to refine future vaccine strategy.