To establish a diagnostic index for predicting enzootic bovine leukosis (EBL), proviral bovine leukemia virus (BLV) copies in whole blood, lymph nodes and spleen were examined by quantitative real-time PCR (qPCR). Cattle were divided into two groups, EBL and BLV-infected, based on meat inspection data. The number of BLV copies in all specimens of EBL cattle was significantly higher than those of BLV-infected cattle (p < 0.0001), and the number of BLV copies in the lymph nodes was particularly large. Over 70 % of the superficial cervical, medial iliac and jejunal lymph nodes from EBL cattle had more than 1,000 copies/10 ng DNA, whereas lymph nodes from BLV-infected cattle did not. These findings suggest that the cattle harboring more than 1,000 BLV copies may be diagnosed with EBL.

INTRODUCTION Rotavirus A (RVA) is a major cause of gastroenteritis in infants and young children worldwide. In 2016, RVA caused 128,500 deaths in children under 5 years of age globally (1). Although most of these deaths occurred in developing countries, RVA imposes a huge burden even in developed countries, including Japan (2-4). Live attenuated RVA vaccines were introduced in Japan in 2011 (Rotarix ® , GlaxoSmithKline Biologicals, Rixensart, Belgium) and in 2012 (RotaTeq ® , Merck & Co., Inc., Kenilworth, NJ, USA), and while RVA vaccines have proven to be effective (5,6), the selective pressure of a vaccine may induce an epidemic strain shift (7-10). The RVA genome contains 11 gene segments of double-stranded RNA that encode six structural (VPs) and six nonstructural proteins (NSPs) (11). To classify RVAs, a specific genotype is assigned to each of the 11 genome segments, according to predefined nucleotide sequence identity cutoff values (12-14). The classification system denotes the VP7-VP4-VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5 6 genes of an RVA strain as a descriptor Gx-P[x]-Ix-Rx-Cx-Mx-Ax-Nx-Tx-Ex-Hx (x indicating genotype number),

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Although norovirus (NoV) is the major cause of gastroenteritis, with the largest number of NoV food poisoning cases in Japan, limited information is available regarding NoV detection in food. This study aimed to detect NoV in food samples during the 2015–2016 suspected foodborne outbreaks in Tokyo; 352 food samples from 64 NoV food poisoning outbreaks were collected. Bacterial culturing was performed for sample pretreatment and real‐time reverse transcription polymerase chain reaction was conducted for NoV screening. The NoV detection rate was 1·7% (6/352). NoV‐positive food samples included leftover boxed lunch, mackerel fillet (foodstuff), aburi salmon slice (partially seared salmon slice), raw tuna as a chirashizushi ingredient, raw amberjack as a sushi topping and ice for drinks. Since fresh fish as sushi toppings or ingredients and ice were consumed without heating, they may present a higher risk of viral infection. NoV‐positive food samples were obtained from five outbreaks, wherein food handlers were NoV‐positive in four. Each partial VP1 sequence from food samples matched completely with those in NoV‐positive individuals and food handlers. Hence, food handlers play a potentially important role in food‐based NoV transmission in all five outbreaks; therefore, hygiene education among them is essential to prevent NoV foodborne outbreaks. Significance and Impact of the Study Significance and Impact of the Study: Norovirus (NoV) is a leading cause of foodborne outbreak in Japan. The most frequent route of transmission in NoV foodborne outbreaks is secondary contamination via infected food handlers. However, limited information is available regarding NoV contamination in food samples. This study reports the detection of NoV in food samples to elucidate the source and route of NoV infection leading to outbreaks for 2 years in Tokyo. Our data potentially contribute to education and the development of safe food‐handling strategies among food handlers and employees in the food industry through elucidation of risk factors associated with NoV contamination.

Background and Aim The incidence of acute hepatitis A [AH (A)] is decreasing because of improvements in hygiene; however, cases of sporadic severe hepatitis are still being reported. We assessed the epidemiology of AH (A) in Japan. Methods This was a hospital‐based retrospective study, in which 126 AH (A) patients (96 men [76%], median age 39 [range, 19–66] years) were enrolled. Patients diagnosed with AH (A) before 2001 (n = 79) and after 2001 (n = 47) were compared. Results The incidence of AH (A) showed peaks in 1990, 1999, and 2018. After 2001, one patient had hepatitis B virus, four had human immunodeficiency virus, and three had syphilis coinfections. Before and after 2001, HAV was transmitted, respectively, by raw oysters (28% and 26%), overseas travel (19% and 28%), and sexual contact (0% and 19%) (P < 0.01). The frequencies of symptoms were appetite loss (51% and 32%), fever (63% and 81%), and diarrhea (3% and 13%) (all P < 0.05), respectively. On admission, the median levels of alanine aminotransferase (1455 and 3069 U/L) and γ‐glutamyl transpeptidase (221 and 345 U/L) were significantly higher (P < 0.01), and the prothrombin time (77.5% and 65.9%) and platelet count (22.7 and 16.4 × 10/μL) were significantly lower after 2001 (P < 0.05). A time to normalization of the bilirubin level ≥ 30 days was associated with older age and a diagnosis of AH (A) after 2001. Conclusions Outbreaks and severe AH (A) cases due to sexual transmission have been reported recently. It is necessary to examine their sexual behavior and other sexual infection.

The genetic characteristics of Norovirus GII.17 were evaluated. Phylogenetic analysis and comparisons of amino acid (Aa) substitutions and nonsynonymous (NS) substitutions/site/year were performed. The complete VP1 sequence of Tokyo/27-3/1976 clustered independently with GII.P17_GII.17 strains. Aa substitutions were mainly accumulated in the P2 domain. NS substitutions/site/year for Tokyo/27-3/1976 compared to Kawasaki323/2014 and Kawasaki308/2015 were 0.57 × 10 and 0.78 × 10 , respectively; for GII.4 Sydney/NSW0514/2012 compared to CHDC2094/1974 and CHDC5191/1974 were 0.93 × 10 and 1.06 × 10 , respectively. These findings imply that evolutionary diversity in the VP1 of GII.17 might be strictly constrained in contrast to that of GII.4.

, four food poisoning outbreaks occurred in Tokyo, involving ten schools. Shredded dried laver seaweed processed by a single food manufacturer in December 2016 was provided in common for the school meals that caused all four outbreaks. Of 4,209 persons exposed, 1,193 28.3 had symptoms of gastroenteritis. Norovirus NoV GII was detected in 207 78.1 of 265 cases by real-time RT-PCR. Thirty-one shredded dried laver seaweed samples were examined and seven 22.6 of them were positive for NoV GII. PCR fragments of NoV ORF1/2 junction region 302 bp from seven shredded dried laver seaweed samples and 20 clinical samples derived from the four outbreaks were sequenced. All of them displayed complete homology, and the genotype was classified as GII.17. A nearly full-length sequence 7,420 bp of NoV RNA derived from a case was obtained by next-generation sequencer analysis and phylogenetic analysis indicated that this strain belongs to the same cluster as Hu/GII/JP/2015/GII.P17_GII.17/Kawasaki308. Thus, our investigation elucidated that the causative agent of these four serial food poisoning outbreaks was NoV GII.17 and the infectious source was a single batch of shredded dried laver seaweed. The water activity of the shredded dried laver seaweed was found to be 0.119 to 0.129. It was epidemiologically clarified that NoV does not lose infectivity for about two months even in the dry state. We conclude that a large diffuse outbreak of food poisoning caused by NoV GII.17 contamination of shredded dried laver seaweed had occurred in Tokyo. Our elucidation of the causative agent indicated that the food poisoning outbreaks in multiple areas of Japan, including Tokyo, during January to February 2017 were caused by the same contaminated food.

Asymptomatic carriers have a major influence on the spreading of norovirus infections. The objective of this study was to examine the characteristics of patients and asymptomatic carriers affected by norovirus-related community gastroenteritis outbreaks. No significant difference between the two groups was observed in terms of the number of norovirus-antibody complexes with respect to total numbers. Principal coordinates analysis of the intestinal flora based on β-diversity analysis, revealed a different bacterial composition between patients and asymptomatic carriers, particularly regarding the genera Pseudomonas, Bacteroides, and Erwinia, as well as the Ruminococcaceae family. Although the proportional changes between these intestinal microorganisms were not sufficient to explain gastroenteritis symptoms, they represent possible markers shared by asymptomatic norovirus carriers.