An outbreak of influenza A(H1N1)pdm09 antigenic variants exhibiting cross-resistance to oseltamivir and peramivir in an elementary school in Japan, September 2024.

An outbreak of influenza A(H1N1)pdm09 viruses exhibiting cross-resistance to oseltamivir and peramivir occurred in Yokohama, Japan, in September 2024. Among 24 students in a class, 11 were diagnosed with influenza or influenza-like illness, and viruses harbouring the NA H275Y and HA Q210H substitutions were isolated from four. Deep sequencing analysis confirmed the clonal spread of these mutants.

Monitoring Influenza C and D Viruses in Patients With Respiratory Diseases in Japan, January 2018 to March 2023.

Background: Influenza viruses can cause zoonotic infections that pose public health risks. Surveillance of influenza A and B viruses is conducted globally; however, information on influenza C and D viruses is limited. Longitudinal monitoring of influenza C virus in humans has been conducted in several countries, but there has been no long-term monitoring of influenza D virus in humans.

Influence of herd immunity on norovirus: a long-term field study of repeated viral gastroenteritis outbreaks at the same facilities.

Background: Viral acute gastroenteritis (AG) is detected worldwide annually. Outbreaks caused by viruses associated with gastroenteritis have been reported repeatedly at the same facilities in Yokohama, Japan over several years. We investigated the statuses of these repeated outbreaks to consider herd immunity at the facility level.

Ideal Test Time for Coronavirus Disease 2019 Contact Tracing.

Background: Epidemiological contact tracing is a powerful tool to rapidly detect SARS-CoV-2 infection in persons with a close contact history with COVID-19-affected patients. However, it remains unclear whom and when should be PCR tested among the close contact subjects.

Methods: We retrospectively analyzed 817 close contact subjects, including 144 potentially SARS-CoV-2-infected persons.

Highly specific monoclonal antibodies and epitope identification against SARS-CoV-2 nucleocapsid protein for antigen detection tests.

The ongoing coronavirus disease 2019 (COVID-19) pandemic is a major global public health concern. Although rapid point-of-care testing for detecting viral antigen is important for management of the outbreak, the current antigen tests are less sensitive than nucleic acid testing. In our current study, we produce monoclonal antibodies (mAbs) that exclusively react with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and exhibit no cross-reactivity with other human coronaviruses, including SARS-CoV.

Increased risk of rhinovirus infection in children during the coronavirus disease-19 pandemic.

Background: Coronavirus disease (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first detected in Japan in January 2020 and has spread throughout the country. Previous studies have reported that viral interference among influenza virus, rhinovirus, and other respiratory viruses can affect viral infections at the host and population level.

Methods: To investigate the impact of COVID-19 on influenza and other respiratory virus infections, we analyzed clinical specimens collected from 2244 patients in Japan with respiratory diseases between January 2018 and September 2020.

Recent Molecular Evolution of Human Metapneumovirus (HMPV): Subdivision of HMPV A2b Strains.

Human metapneumovirus (HMPV) is a major etiological agent of acute respiratory infections in humans. HMPV has been circulating worldwide for more than six decades and is currently divided into five agreed-upon subtypes: A1, A2a, A2b, B1, and B2. Recently, the novel HMPV subtypes A2c, A2b1, and A2b2 have been proposed.

Early combination treatment with baloxavir and peramivir for hospitalized adults with influenza A in Yokohama, Japan.

Baloxavir marboxil is a new anti-influenza drug, but data on the clinical efficacy of a combination treatment of baloxavir and peramivir is scarce. We conducted a single-center retrospective analysis comparing the mortality of a combination of baloxavir and peramivir (B & P, n = 10) and peramivir without baloxavir (P-mono, n = 132) in hospitalized adults with influenza A between 2011 and 2019 in Yokohama City, Japan. Sequencing analysis was conducted in the B & P group to check the I38 mutation in polymerase acidic protein which is associated with baloxavir resistance.

Environmental Surveillance Can Dynamically Track Ecological Changes in Enteroviruses.

Environmental surveillance can be used to trace enteroviruses shed from human stool using a sewer network that is independent of symptomatic or asymptomatic infection. In this study, the local transmission of enteroviruses was analyzed using two wastewater treatment plants, which were relatively close to each other (15 km), designated as sentinels. Influent was collected at both sentinels once a month from 2013 to 2016, and viruses were isolated.

Predominant Detection of the Subgroup A2b Human Metapneumovirus Strain with a 111-Nucleotide Duplication in the G gene in Yokohama City, Japan in 2018.

Human metapneumovirus (HMPV) has been a major causative agent of acute respiratory infections in humans. Recently, two types of variant A2b subtype HMPV strains possessing a 111- or 180-nucleotide duplication (nt-dup) in the G gene (HMPV A2b and HMPV A2b, respectively) were detected in Japan, Spain, Vietnam, and China. Our surveillance for infectious agents in Yokohama City, Japan revealed that the HMPV A2b strain became predominant in Yokohama City in 2018.

Hepatitis A Outbreak Among Men Who Have Sex With Men, Yokohama, Japan, January to May 2018.

Between January and May in 2018, 17 male cases of hepatitis A were reported in Yokohama, Japan. Of these, 14 identified as men who have sex with men. The viral sequence in this outbreak was same as that of the recent European and Taiwanese outbreaks strain.

Isolation and Complete Genome Sequencing of Zika Virus Imported from the Dominican Republic to Japan.

Zika virus (ZIKV) infection has been documented within Central and South America, Asia, and Africa. Here we report the isolation of virus from a patient infected with ZIKV returning to Japan from the Dominican Republic. The ZIKV strain was imaged by electron microscopy and its complete genome sequence was analyzed.

A novel 111-nucleotide duplication in the G gene of human metapneumovirus.

In 2017, novel human metapneumovirus (HMPV) A2b subgroup strains with a 111-nucleotide duplication in the G gene was detected by the present team. These strains were related to previously identified HMPV A2b strains with a 180-nucleotide duplication; however, they appeared to be different strains, produced by an independent duplication event. The recent evolution of HMPV suggests that careful monitoring of this virus is required.

180-Nucleotide Duplication in the G Gene of A2b Subgroup Strains Circulating in Yokohama City, Japan, since 2014.

(HMPV), a member of the family , was first isolated in 2001. Seroepidemiological studies have shown that HMPV has been a major etiological agent of acute respiratory infections in humans for more than 50 years. Molecular epidemiological, genetic, and antigenetic evolutionary studies of HMPV will strengthen our understanding of the epidemic behavior of the virus and provide valuable insight for the control of HMPV and the development of vaccines and antiviral drugs against HMPV infection.

Norovirus genotype distribution in outbreaks of acute gastroenteritis among children and older people: an 8-year study.

Background: Noroviruses (NoVs) are the most frequent cause of acute gastroenteritis worldwide among people of all ages and the leading cause of gastrointestinal disease outbreaks in various settings. To clarify the differences in epidemic situations among different settings, we investigated epidemiological trends and the distribution of NoV genotypes in Yokohama, Japan.

Methods: Between September 2007 and August 2015, 746 outbreaks of NoV gastroenteritis were reported in kindergarten/nursery schools (K/Ns), primary schools (PSs), and nursing homes for the aged (NHs).

Four Cases of Autochthonous Dengue Infection in Japan and 46 Imported Cases: Characteristics of Japanese Dengue.

Objective: A dengue outbreak occurred in Japan 2014. We investigated the characteristics of dengue infection among Japanese.

Methods: We investigated the medical charts retrospectively.

Genetic Analysis of Norovirus GII.4 Variant Strains Detected in Outbreaks of Gastroenteritis in Yokohama, Japan, from the 2006-2007 to the 2013-2014 Seasons.

Noroviruses (NoVs) are the leading cause of acute gastroenteritis, both in sporadic cases and outbreaks. Since the 1990s, the emergence of several GII.4 variants has been reported worldwide.

Detection and Genetic Analysis of Noroviruses and Sapoviruses in Sea Snail.

An outbreak of acute gastroenteritis occurred at a restaurant in Yokohama in December 2011. Because many of the customers had consumed raw sea snail, sea snail was suspected to be the source of this outbreak. To determine whether sea snail contains Norovirus (NoV) or Sapovirus (SaV), we analyzed 27 sea snail samples collected over 5 months (May, June, August, October, and December 2012) and 59.

Nucleotide Correlations Between Rotavirus C Isolates in Clinical Samples from Outbreaks and in Sewage Samples.

Rotavirus C (RVC) is detected in both sporadic cases and outbreaks of gastroenteritis worldwide. However, the epidemic dynamics of RVC in populations remain poorly understood because the detection rate is low. In this study, raw sewage samples were collected from a wastewater treatment plant in Yokohama, Japan, over 5 years, in 12-month period from September to August, to identify the RVC strains in these samples and compare them with the RVC strains circulating in the population.

Epidemiological and genetic analysis of human group C rotaviruses isolated from outbreaks of acute gastroenteritis in Yokohama, Japan, between 2006 and 2012.

Group C rotavirus (GCRV) infection has been described in several parts of the world, predominantly as sporadic cases of acute gastroenteritis. Little is known about the yearly changes in the GCRV strains from diarrheal outbreaks. Stool samples collected from outbreaks of acute gastroenteritis in Yokohama, Japan, between 2006 and 2012 that were negative for norovirus, sapovirus, and group A rotavirus, were screened for GCRV using a reverse passive hemagglutination method.

An outbreak of food-borne gastroenteritis due to sapovirus among junior high school students.

The human sapovirus (SaV) causes acute gastroenteritis mainly in infants and young children. A food-borne outbreak of gastroenteritis associated with SaV occurred among junior high school students in Yokohama, Japan, during and after a study trip. The nucleotide sequences of the partial capsid gene derived from the students exhibited 98% homology to a SaV genogroup IV strain, Hu/Angelholm/SW278/2004/SE, which was isolated from an adult with gastroenteritis in Solna, Sweden.