The aim of this study was to describe the clinical, histopathological, and immunohistochemical characteristics of monkeypox (MPX) and offer meaningful insights into the clinicopathological characteristics. Eight males who have sex with males and were diagnosed with MPX based on positive results from MPX virus (MPXV)-specific polymerase chain reaction were recruited. Skin biopsies were obtained from four selected lesions, including typical and atypical forms. Histopathological examinations of atypical solitary ulceration revealed infiltrating inflammatory cells, predominantly plasma cells and lymphocytes forming a "sleeve" around the superficial vessels of the dermis. These features may be misinterpreted as indicative of cutaneous syphilis. In addition, typical pustular lesions had a central necrotic epidermis accompanied by a perivascular inflammatory infiltrate dominated by neutrophils, as well as ballooning and reticular degeneration of keratinocytes. Additionally, multinucleated keratinocytes and eosinophilic cytoplasmic inclusions (Guarnieri bodies) were observed. Importantly, this study represents a pioneering report on the immunohistochemical localization of MPXV A29 and A35 proteins in skin lesions, distinguishing it from previous studies that focused on detecting vaccinia virus proteins. The anti-MPXV A29 antibody had intense cytoplasmic staining, specifically within the affected keratinocytes in the adjacent epidermis and hair follicles, thereby contributing to the diagnosis of MPX, particularly in individuals with atypical skin lesions.

Japanese spotted fever (JSF) is a tick-borne rickettsial disease prevalent in western Japan with an increasing incidence and geographical distribution. This retrospective study aimed to describe the clinical features of JSF and identify factors associated with its severe form. We included adult patients with laboratory-confirmed JSF in the Nagasaki Prefecture between 2010 and 2021. Severe JSF was defined as an altered mental status, low blood pressure, or low oxygen saturation. In total, 65 JSF cases were diagnosed. Common symptoms included fever (87%), rash (48%), and fatigue (48%), with eschars detected in 50 (79.4%) patients. Thirty-eight (60.3%) patients were initially diagnosed with non-JSF conditions. Twenty-one (33.3%) patients were categorized as having severe JSF, including one death. Prehospital factors associated with severe JSF included age ≥75 (adjusted odds ratio [aOR] 37.53, 95% confidence interval [CI] 3.03–465.38), male sex (aOR 26.5, 95% CI 4.23–166.00), and a treatment delay ≥4 days from onset (aOR 5.96, 95% CI 1.13–31.60). This study highlights the diagnostic challenges of JSF owing to its non-organ-specific clinical presentation. Delayed initial treatment, advanced age, and male sex significantly increase the risk of disease severity. It is crucial to raise awareness of JSF among clinicians and residents in endemic areas.

Getah virus (GETV), belonging to the genus Alphavirus within the family Togaviridae, is a mosquito-borne virus that causes fever, rash, edema in horses, fatalities, and pregnancy disorders in pigs. It has caused occasional outbreaks in horse populations in Japan, China, and India, and the endemic areas are gradually expanding, particularly in Asia and Oceania. In this study, we isolated a new GETV strain from Culex tritaeniorhynchus mosquitoes collected in Nagasaki Prefecture, Japan, in 2022. Phylogenetic analysis demonstrated that this new strain, 22IH8, was more closely related to previous Chinese strains than to the strains prevalent in Japan in the 2010s. Furthermore, some amino acid substitutions in the viral proteins of strain 22IH8 were similar to those in previous Chinese strains. These results indicate that strain 22IH8 may have recently invaded the Japanese archipelago from mainland Asia. The antiserum against the current vaccine strain MI-110 demonstrated high neutralization activity against the strain 22IH8, indicating the efficiency of the current vaccine for horses in Japan.

Although a live-attenuated yellow fever (YF) vaccine is known to elicit durable immunity, antibody titers may wane after vaccination. This study evaluated long-term immunity after vaccination against YF among individuals who resided in Korea and were vaccinated with YF virus- 17D prior to international travel. Serum was collected between December 2018 and December 2019 at the National Medical Center, Republic of Korea, from YF vaccine recipients who had been vaccinated for more than five years prior to sample collection. Long-term immunity against YF was assessed using three serological assays: IgG enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), and the focus reduction neutralization test (FRNT). Sixty-seven patients were enrolled in this study. The overall positivity rates for 50% focus reduction neutralization test (FRNT₅₀ ), IFA, and ELISA in a time-variable cross-sectional sample of the cohort were 97.0%, 86.6%, and 26.9%, respectively. While 93.8% (15/16) of samples collected ≥10 years post-vaccination remained positive by FRNT₅₀ , a significant inverse correlation was observed between FRNT₅₀ titer and interval after vaccination (R = − 0.385, P = 0.001). Humoral immunity against YF was well preserved among Korean individuals who were vaccinated more than five years ago. IFA testing yielded results similar to those of FRNT₅₀ testing, which may justify the further development of IFA to screen for waning immunity among those with previous YF vaccination.

In 2021, vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were developed and the Omicron variant emerged. This study compared the characteristics, treatments, and mortality of patients with coronavirus disease 2019 (COVID-19) between 2022 and 2020–2021, using administrative claims data linked including vaccine records in a Japanese city. Patients who underwent COVID-19 antigen or polymerase chain reaction tests and were diagnosed with COVID-19 were identified. Patient characteristics, treatments, and mortality were compared between 2022 and 2020–2021 among those diagnosed with COVID-19. We identified 26,262 patients with COVID-19. The mortality in 2022 was lower than that in 2020–2021 (0.6% vs. 1.7%; P < 0.01). Patients in 2022 were significantly less likely to receive oxygen therapy, high-flow nasal oxygenation, mechanical ventilation, steroids, and tocilizumab than those in 2020–2021. Among the deceased, the proportion of those aged ≥65 years was significantly higher in 2022 than in 2020–2021 (98.4% vs. 88.6%). The logistic regression analysis indicated, older age, male sex, and ≥3 comorbidities were associated with higher mortality, whereas ≥3 vaccinations were associated with lower mortality. Patients with COVID-19 in 2022 were less likely to require respiratory care or succumb to the disease. Older patients were more likely to die in 2022 than in 2020–2021.

Immunofluorescence methods using cell lines to detect seasonal human coronavirus (HCoV)-OC43 in nasopharyngeal swab specimens have not yet been established. A human rectal adenocarcinoma cell line (HRT-18) was exposed to the specimens obtained from patients with upper respiratory tract infections. Immunofluorescence staining was conducted using a combination of human serum containing an HCoV-OC43 anti-spike protein antibody and a fluorescence-labeled anti-human antibody. Positive staining in HRT-18 cells was detected after exposure to specimens obtained from nine of eleven patients in whom HCoV-OC43 RNA was detected using the FilmArray method. Increased viral RNA levels in the supernatant were also detected in HRT-18 cells exposed to specimens obtained from four of five patients. In contrast, positive staining was not detected in HRT-18 cells exposed to six patient specimens that tested negative for RNA from 17 types and subtypes of respiratory viruses, including HCoV-OC43. Cells inoculated with the established strain HCoV-OC43 (ATCC VR-759) also showed positive staining. These findings suggest that replication-competent HCoV-OC43 in the specimens can be detected via immunofluorescence staining of HRT-18 cells with human serum. Using this method, positive staining for viruses other than HCoV-OC43 may be obtained.

Helicobacter pylori, Epstein-Barr virus (EBV), and human papillomavirus (HPV) are three pathogens associated with various human cancers. This study aimed to investigate the role of these pathogens in gastric cancer in a Moroccan population. A retrospective study was conducted with participants attending the Gastroenterology Department of Hassan II University Hospital in Fez. In total, 279 participants were enrolled in this study. Helicobacter pylori, EBV, and HPV were detected and genotyped using polymerase chain reaction. Significant associations have been established between H. pylori and EBV and gastric cancer. A total of 93.4% and 43.3% of gastric cancer cases were related to H. pylori and EBV, respectively (P ≤ 0.01). Helicobacter pylori-EBV co-infection was responsible for 31.6% of gastric cancer cases (P < 0.01). Correlation between pathogen genotypes and gastric cancer showed that 54.6% of gastric cancer EBV positive cases had a 30 bp deletion in the LMP1 gene, whereas 16% of gastric cancer cases had high-risk HPV genotypes (P = 0.21). These results highlight the possible role of co-infection in gastric cancer development.

The effect of the antibodies elicited by bivalent mRNA vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (the original strain and Omicron variant BA.1) on preventing coronavirus disease 2019 (COVID-19) onset during the XBB variant dominance remains unknown. We conducted a prospective cohort study at Chiba University Hospital and examined healthcare workers who received the Pfizer-BioNTech bivalent mRNA COVID-19 vaccine (targeting the original and Omicron BA.1) as their sixth dose of COVID-19 vaccine. The serum antibodies against SARS-CoV-2 spike (S) protein were measured quantitatively. Participants who were not infected during the 60-day observation period following the sixth vaccination had significantly higher S antibody titers than those who were newly infected (27,756 U/mL, 95% confidence interval [CI] 24,988–30,831 U/mL vs. 15,321 U/mL, 95% CI 10,824–21,688 U/mL; P < 0.05). S antibody titer ≥15,500 U/mL decreased the risk of infection by 84%. Neutralizing antibody titers against the XBB.1.16 and XBB.1.42 variants were higher in age- and sex-matched non-infected individuals than in newly infected individuals during the post-vaccination observation period. S antibody titers were highly correlated with neutralizing antibody titers. In conclusion, after the sixth vaccination with a bivalent mRNA COVID-19 vaccine, high S antibody titers correlated with disease prevention, even in the presence of the XBB variants.

Evidence regarding the types of masks that are effective in preventing infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is limited. We identified the mask types that were effective against SARS-CoV-2 infection in a cluster setting in Japan. Data from a cluster of employees with coronavirus disease 2019 at a manufacturing company in mid-August 2021 were retrospectively reviewed. A total of 87 employees who reported the type of mask worn were included. The types of masks were dichotomized into non-woven masks or other types of masks, such as cloth or urethane masks. The association between mask type and SARS-CoV-2 infection was determined using logistic regression analysis after adjusting for potential confounders. Participants who wore non-woven masks were less likely to be infected with SARS-CoV-2 (9.7%) than those who wore other types of masks (26.7%). After adjusting for potential confounders, wearing a non-woven mask was significantly associated with a reduced risk of infection compared to wearing other types of masks (odds ratio, 0.10; 95% confidence interval, 0.01–0.80). Non-woven masks were more effective in preventing SARS-CoV-2 infection in a cluster setting than other types of masks, such as cloth or urethane masks.

Japan’s National Epidemiological Surveillance of Infectious Diseases (NESID) has implemented a warning system for detecting epidemics in smaller districts, such as public health center (PHC) areas. This system is applied to influenza and pediatric infectious diseases. Respiratory syncytial virus (RSV) infection is not included but its incorporation is needed for effective early epidemic detection. We aimed to propose criterion values for an epidemic warning system related to RSV infection within PHC areas. We analyzed the weekly number of RSV infection cases reported by sentinel medical institutions (SMIs) in the NESID from 2015 to 2019. Weekly cases per SMI in the PHC area were set to establish an index for epidemic warnings. We determined criteria for issuing an epidemic warning by identifying distribution percentiles within the index. Setting the critical values for the onset and end of the epidemic warning at 5 and 2, respectively, yielded an approximately 5% annual proportion of PHC areas with an epidemic warning, which aligns with previously accepted frequency criteria for epidemic warnings. The 5-year (2015–2019) RSV infection epidemic trend showed that the set critical values were appropriate. Using these values could assist with issuing warnings regarding potential RSV infection epidemics in Japan.