Full genome-based characterization of an Asian G3P[6] human rotavirus strain found in a diarrheic child in Japan: Evidence for porcine-to-human zoonotic transmission.

Human rotavirus strains having the unconventional G3P[6] genotype have been sporadically detected in diarrheic patients in different parts of the world. However, the full genomes of only three human G3P[6] strains from Asian countries (China, Indonesia, and Vietnam) have been sequenced and characterized, and thus the exact origin and evolution of G3P[6] strains in Asia remain to be elucidated. Here, we sequenced and characterized the full genome of a G3P[6] strain (RVA/Human-wt/JPN/SO1199/2020/G3P[6]) found in a stool sample from a 3-month-old infant admitted with acute gastroenteritis in Japan. On full genomic analysis, strain SO1199 was revealed to have a unique Wa-like genogroup configuration: G3-P[6]-I5-R1-C1-M1-A8-N1-T1-E1-H1. VP6 genotype I5 and NSP1 genotype A8 are commonly found in porcine rotavirus strains. Furthermore, phylogenetic analysis demonstrated that all 11 genes of strain SO1199 were closely related to those of porcine and/or porcine-like human rotaviruses and thus appeared to be of porcine origin. Thus, strain SO1199 was shown to possess a porcine-like genomic backbone and thus is likely to be the result of interspecies transmission of a porcine rotavirus strain. Of note is that all 11 genes of strain SO1199 were phylogenetically located in clusters, distinct from those of the previously identified porcine-like human G3P[6] strains from around the world including Asia, suggesting the occurrence of independent porcine-to-human zoonotic transmission events. To our knowledge, this is the first report on full genome-based characterization of a human G3P[6] strain that has emerged in Japan. Our findings revealed the diversity of unconventional human G3P[6] strains in Asia, and provide important insights into the origin and evolution of G3P[6] strains.

Rapid Spread in Japan of Unusual G9P[8] Human Rotavirus Strains Possessing NSP4 Genes of E2 Genotype.

The emergence of unusual G9P[8]-E2 human rotaviruses in the Tokyo metropolitan area, Japan, in 2018 has been reported. During rotavirus strain surveillance in different regions of Japan (Mie, Okayama, and Chiba prefectures), G9P[8]-E2 strains were detected in children with diarrhea from all three prefectures. Here, we characterized the whole genome of seven representative G9P[8]-E2 strains. In the full-genome-based analysis, the seven study strains exhibited a unique genotype configuration with the NSP4 gene of genogroup 2 in a genogroup 1 genomic backbone: G9-P[8]-I1-R1-C1-M1-A1-N1-T1-E2-H1. This genotype constellation was shared by the Tokyo G9P[8]-E2 strains. Phylogenetic analysis showed that all 11 genes, except NSP4, of the seven study strains appeared to have originated from co-circulating Wa-like G9P[8]-E1 strains. In contrast, NSP4 appeared to have originated from the co-circulating DS-1-like G2P[4]-E2 strains. Thus, G9P[8]-E2 strains appear to be derived through reassortment between G9P[8]-E1 and G2P[4]-E2 strains in Japan. Notably, the seven study G9P[8]-E2 strains and Tokyo G9P[8]-E2 strains were revealed to have 11-segment genomes almost indistinguishable from one another in their sequences (99.3-100%), indicating all these G9P[8]-E2 strains had a common origin. To our knowledge, this is the first description of the rapid spread of G9P[8]-E2 strains across a country.

Molecular Epidemiology of Norovirus (NoV) Infection in Mie Prefecture: The Kinetics of Norovirus Antigenemia in Pediatric Patients.

Few studies have shown the presence of norovirus (NoV) RNA in blood circulation but there is no data on norovirus antigenemia. We examined both antigenemia and RNAemia from the sera of children with NoV infections and studied whether norovirus antigenemia is correlated with the levels of norovirus-specific antibodies and clinical severity of gastroenteritis. Both stool and serum samples were collected from 63 children admitted to Mie National Hospital with acute NoV gastroenteritis. Norovirus antigen and RNA were detected in sera by ELISA and real-time RT-PCR, respectively. NoV antigenemia was found in 54.8% (34/62) and RNAemia in 14.3% (9/63) of sera samples. Antigenemia was more common in the younger age group (0-2 years) than in the older age groups, and most patients were male. There was no correlation between stool viral load and norovirus antigen (NoV-Ag) levels (rs = -0.063; Cl -0.3150 to 0.1967; p = 0.6251). Higher levels of acute norovirus-specific IgG serum antibodies resulted in a lower antigenemia OD value (n = 61; r = -0.4258; CI -0.62 to -0.19; p = 0.0006). Norovirus antigenemia occurred more commonly in children under 2 years of age with NoV-associated acute gastroenteritis. The occurrence of antigenemia was not correlated with stool viral load or disease severity.

Salivary cytomegalovirus excretion in children in daycare centers and home care facilities in Japan.

Cytomegalovirus (CMV) is the most common cause of congenital viral infection in developed countries. The incidence of in utero infection is high in pregnant women who are CMV antibody negative. An important infection route is in contact with children who attend daycare centers (DCCs). However, there are few reports on CMV excretion in children at DCCs in Japan. Saliva samples were collected twice during a 6-month interval from children attending one of two DCCs (DCC1 and DCC2 groups) and from those receiving home care (HC group). The samples were used to quantitatively evaluate CMV using real-time polymerase chain reaction and to determine glycoprotein B (gB) genotypes. The percentage of subjects who demonstrated CMV excretion in either the first or second sample collection was higher in the DCC groups than in the HC group, with incidences in the DCC1, DCC2, and HC groups of 53.4% (n = 47 of 88), 23.9% (n = 16 of 67), and 12.7% (n = 7 of 55), respectively. Compared with the DCC2 group, the DDC1 group had a higher incidence of CMV excretion and included more subjects with a high number of viral copies. In both DCC groups, the incidence of CMV excretion was highest in children younger than 3 years of age. In all three groups, the predominant genotypes were gB1 and gB3. Based on the higher incidence of CMV excretion in the DCC groups compared with the HC group, it is considered that CMV infection is acquired mainly in DCCs in children under the age of 3.

Characterization of an Unusual DS-1-Like G8P[8] Rotavirus Strain from Japan in 2017: Evolution of Emerging DS-1-Like G8P[8] Strains through Reassortment.

The emergence of unusual DS-1-like intergenogroup reassortant rotaviruses with a bovine-like G8 genotype (DS-1-like G8P[8] strains) has been reported in several Asian countries. During the rotavirus surveillance program in Japan in 2017, a DS-1-like G8P[8] strain (RVA/Human-wt/JPN/SO1162/2017/G8P[8]) was identified in 43 rotavirus-positive stool samples. Strain SO1162 was shown to have a unique genotype constellation, including genes from both genogroup 1 and 2: G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis revealed that the VP1 gene of strain SO1162 appeared to have originated from DS-1-like G1P[8] strains from Thailand and Vietnam, while the remaining 10 genes were closely related to those of previously reported DS-1-like G8P[8] strains. Thus, SO1162 was suggested to be a reassortant strain that acquired the VP1 gene from Southeast Asian DS-1-like G1P[8] strains on the genetic background of co-circulating DS-1-like G8P[8] strains. Our findings provide important insights into the evolutionary dynamics of emerging DS-1-like G8P[8] strains.

Characterization of unusual DS-1-like G3P[8] rotavirus strains in children with diarrhea in Japan.

The emergence and rapid spread of novel DS-1-like intergenogroup reassortant rotaviruses having the equine-like G3 genotype (DS-1-like G3P[8] strains) have been recently reported from several countries. During rotavirus surveillance in Japan in 2015-2016, three DS-1-like G3P[8] strains were identified from children with severe diarrhea. In the present study, we sequenced and characterized the full genomes of these three strains. On full-genomic analysis, all three strains showed a unique genotype constellation including both genogroup 1 and 2 genes: G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis revealed that each of the 11 genes of the three strains was closely related to that of Japanese DS-1-like G1P[8] and/or Japanese equine-like G3P[4] human strains. Thus, the three study strains were suggested to be reassortants that acquired the G3-VP7 gene from equine G3 rotaviruses on the genetic background of DS-1-like G1P[8] strains. Our observations will provide important insights into the evolutionary dynamics of emerging DS-1-like G3P[8] strains.

Laboratory Diagnosis of Breakthrough Varicella in Children.

BACKGROUND: Breakthrough varicella (BV) develops in vaccinated persons as a result of infection by wild-type varicella-zoster virus more than 42 days after varicella vaccination. The clinical symptoms are atypical, and clinical diagnosis can be difficult. We investigated laboratory-based diagnostic methods that are relatively simple and highly precise to conduct accurate surveillance. SUBJECTS AND METHODS: We enrolled 42 patients with suspected BV at 2 pediatric hospitals and performed a real-time polymerase chain reaction (PCR) on the skin lesions to confirm the BV diagnosis. We performed PCR on saliva and blood collected during the acute phase, as well as direct fluorescent antibody (DFA) imaging on lesions, and measured varicella-zoster virus immunoglobulin (Ig) G and IgM during the acute and convalescent phases. RESULTS: We confirmed the BV diagnosis in 31 of 42 enrolled patients. The sensitivity of DFA imaging of the lesion, and PCR of saliva and blood were 93.5%, 87.1% and 61.3%, respectively. IgM was detected in 12.9% of patients during the acute phase and in 65.5% during the convalescent phase. IgG increased more than 4-fold in 86.2% of patients between the acute and convalescent phases. The sensitivity and specificity of the assay were 83.9% and 81.8%, respectively, when the diagnostic criteria for IgG were set to greater than 20 during the acute phase. CONCLUSIONS: The gold standard of laboratory-based diagnosis of BV has been the PCR of samples taken from lesions. However, DFA of the lesion showed equivalent sensitivity when compared with PCR. PCR using saliva samples is an effective, noninvasive method of diagnosis. We found that high values of IgG during the acute phase can aid in the diagnosis of BV.