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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.

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.

ABSTRACT Human astroviruses (HAstVs) are important causative pathogens of acute gastroenteritis (AGE) in children worldwide. MLB and VA HAstVs, which are genetically distinct from the previously known classic HAstVs, have been detected since 2008. To investigate the role of HAstVs in AGE, we conducted molecular detection and characterization of HAstVs circulating in children with AGE in Japan from 2014 to 2021. Out of 2,841 stool samples, HAstVs were detected in 130 (4.6%). MLB1 was the predominant genotype detected (45.4%), followed by HAstV1 (39.2%), MLB2 (7.4%), VA2 (3.1%), HAstV3 (2.3%), HAstV4, HAstV5, and MLB3 (0.8% each). The results demonstrated that HAstV infection in pediatric patients in Japan was dominated by the two major genotypes MLB1 and HAstV1, with a small proportion of other genotypes. The overall infection rates of MLB and VA HAstVs were higher than those of classic HAstVs. The HAstV1 strains detected in this study belonged solely to lineage 1a. The rare MLB3 genotype was detected for the first time in Japan. All three HAstV3 strains belonged to lineage 3c based on the ORF2 nucleotide sequence and were shown to be recombinant strains. IMPORTANCE HAstVs are one of the pathogens of viral AGE and are considered the third most common viral agents of AGE after rotavirus and norovirus. HAstVs are also suspected to be the causative agents of encephalitis or meningitis in immunocompromised patients and elderly persons. However, little is known about the epidemiology of HAstVs in Japan, especially that of MLBs and VA HAstVs. This study demonstrated epidemiological features and molecular characterization of human astroviruses encompassing a 7-year study period in Japan. This study highlights the genetic diversity of HAstV circulating in pediatric patients with acute AGE in Japan.