Japanese journal of infectious diseases最新文献

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has repeatedly undergone mutations since its emergence, based on which it has been assumed that there was a change in its characteristic, including virulence or antigenicity. In this study, we investigated the viral load in the nasopharyngeal samples of patients with SARS-CoV-2 in Gunma prefecture, Japan, from April 2, 2020, to April 1, 2023. The amount of virus in samples in the Omicron-variant-prevalent period was higher than that of strains detected in samples before week 50 of 2020, the B.1.1.284-prevalent period, the Alpha-variant-prevalent period, and the Delta-variant- prevalent period. Moreover, among Omicron variants, the sublineage BA.5-prevalent period showed higher amount of virus in the samples than BA.1-prevalent period and BA.2-prevalent period. Hence, the new variant may have been able to release more viruses into the nasopharyngeal samples during the process of repeated mutations, resulting in widespread infection. The amount of virus detected in the nasopharyngeal samples showed an increasing tendency with the evolution of the virus. Therefore, considering that the amount of virus in specimens is also vital factor contributing to the spread of infection, it is important to examine this factor in samples.

Ticks are vectors of tick-borne diseases (TBDs) between humans and wild vertebrates. The relationship between ticks, host vertebrates, and their pathogens should be investigated for the effective control of TBDs. Hence, this study aimed to detect vertebrate DNA in ticks by using molecular methods and identify the species of such ticks collected in Fukuoka Prefecture, which is located in the northern Kyushu area of Japan. Ticks from vegetation were collected by flagging from 2017 to 2023. Out of 152 ticks collected by flagging, 65 (42.8%) were found to have vertebrate DNA. By stage, vertebrate DNAs were detected in 26 of 83 nymphs (31.3%) and 39 of 69 adults (56.5%). Among the host vertebrates, Sika deer was the main blood-feeding source of ticks in Fukuoka Prefecture. Owing to the widespread of deer across this prefecture, control of its population and other wildlife populations could be a countermeasure of reducing TBD risk.

Early and accurate diagnosis of leprosy is important but remains a significant challenge till date. Loop-mediated isothermal amplification (LAMP) is an isothermal process for amplification of nucleic acids at constant temperature and has been used to develop field-friendly tests for many diseases. In the present study, we have described the development of a colorimetric LAMP assay targeting Mycobacterium leprae-specific 450 bp conserved region of the repeat sequences known as RLEP. Furthermore, the amplicons of LAMP were subjected to restriction analysis by the enzyme EcoRV for specificity. This method has the potential to become an accurate and efficient alternative to Sanger sequencing which is currently in use to validate the RLEP amplified products.

Guidelines for sexually transmitted infections recommend oral metronidazole (MNZ) as the first-line treatment option for vaginal trichomoniasis; however, there have been cases of prolonged symptoms or recurrence after treatment. To consider appropriate treatment strategies for refractory vaginal trichomoniasis, we conducted a retrospective cohort study. We reviewed the medical records of patients who tested positive for Trichomonas vaginalis (T. vaginalis) at the National Center for Global Health and Medicine between August 2011 and May 2023. Refractory vaginal trichomoniasis was defined as the failure after the initial MNZ treatment. During the study period, nine cases of vaginal trichomoniasis were identified, six of which were refractory to treatment for T. vaginalis. Four patients were cured with a combination of oral and vaginal tinidazole (TNZ) therapy, one with oral TNZ and one with two doses of MNZ. Possible causes of treatment failure include MNZ-resistant T. vaginalis, reinfection between partners, and infections of other sexual transmitted diseases. However, the fact that TNZ was effective suggests that MNZ-resistant T. vaginalis may have been the cause. Although MNZ resistance testing was not performed in this study, treatment with TNZ should be considered in cases of refractory vaginal trichomoniasis, possibly caused by MNZ-resistant T. vaginalis.

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 but not to respiratory syncytial virus (RSV) infection, whose incorporation is essential for early epidemic detection. We aimed to propose criterion values for the epidemic warning system of 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 for an index for epidemic warnings. We determined the criteria for issuing an epidemic warning by describing the percentiles of the distribution of 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. This aligns with the acceptably implemented frequency of epidemic warnings. The 5-year (2015-2019) RSV infection epidemic trend showed that the set critical values were appropriate. Using these values could help issue warnings regarding potential RSV infection epidemics in Japan.

Evidence about which types of mask are effective in preventing infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is limited. We examined which mask types were effective against SARS-CoV-2 infection in a cluster setting in Japan. We retrospectively reviewed data from a cluster of COVID-19 cases that occurred at a manufacturing company in mid-August 2021. We included a total of 87 individuals who reported the type of mask worn. We dichotomized the types of mask into non-woven masks or other types of mask, such as cloth or urethane masks. We then examined the associations between the mask type and SARS-CoV-2 infection using logistic regression analysis, adjusting for potential confounders. Participants who wore non-woven masks were less likely to be infected with SARS-CoV-2 (9.7%) compared with those who wore other types of mask (26.7%). After adjusting for potential confounders, wearing a non-woven mask was significantly associated with a reduced risk of infection compared with wearing other mask types (odds ratio = 0.10, 95% confidence interval: 0.01 to 0.80). Non-woven masks were found to be more effective in preventing SARS-CoV-2 infection in a cluster setting than other types of mask, such as cloth or urethane masks.

Immunofluorescence methods to detect seasonal human coronavirus (HCoV)-OC43 in nasopharyngeal swab specimens using cell lines 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 with the combination of human serum containing the 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 the eleven patients in which HCoV-OC43 RNA was detected using the FilmArray method. Increased supernatant viral RNA levels 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 seventeen types and subtypes of respiratory viruses, including HCoV-OC43. The cells inoculated with the established strain HCoV-OC43 (ATCC VR-759) also showed positive staining. These findings suggest that the replication-competent HCoV-OC43 in the specimens could be detected via immunofluorescence staining of HRT-18 cells with human serum. It may be possible to obtain positive staining for viruses other than HCoV-OC43 using this method.

Getah virus (GETV), belonging to the genus Alphavirus within the family Togaviridae, is a mosquito-borne virus that causes fever, rash, and edema in horses and fatalities and pregnancy disorders in pigs. It has caused occasional outbreaks in horse populations in Japan, China, and India, and endemic areas are gradually expanding, particularly in Asia and Oceania. In this study, we isolated a new GETV strain from Culex tritaeniorhynchus mosquitoes collected from Nagasaki Prefecture, Japan in 2022. Phylogenetic analysis revealed that this new strain, 22IH8, is 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 found to be common with those in previous Chinese strains. These results suggest that 22IH8 strain may have recently invaded the Japanese archipelago from mainland Asia. The antiserum against the current vaccine strain, MI-110, showed high neutralization activity against the 22IH8 strain indicating the efficiency of the current vaccine for horses in Japan.

While a live-attenuated Yellow fever (YF) vaccine is known to elicit durable immunity, antibody titers may wane after vaccination. This study evaluated the long-term immunity after vaccination against YF among individuals who reside in Korea and received vaccination 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 were vaccinated 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 focus reduction neutralization test (FRNT). Sixty seven subjects were enrolled. The overall positivity rates for FRNT₅₀, IFA and ELISA were 97.0%, 86.6% and 26.9%, respectively, in a time-variable, cross-sectional sample of the cohort. 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 the Korean individuals who were more than five years post-vaccination. IFA testing yielded results similar to FRNT₅₀ testing, which may justify further development of the IFA to screen for waning immunity among those with previous YF vaccination.

The effect of antibodies elicited by bivalent mRNA vaccines (original and omicron BA.1) on preventing coronavirus disease 2019 (COVID-19) onset in the presence of the XBB variant remains unknown. A prospective cohort study conducted at Chiba University Hospital examined healthcare workers who received their sixth vaccination with the Pfizer-BioNTech COVID-19 bivalent mRNA vaccine (original and omicron BA.1). Researchers quantitatively measured serum anti-spike (S) antibody levels. Participants not infected during the 60-day observation period after vaccination had significantly higher S antibody titers than those who were newly infected (27756 U/mL, 95% CI [24988-30831 U/mL] vs. 15321 U/mL, 95% CI [10824-21688 U/mL], p<0.05). The risk of infection decreased by 84% when the S antibody titer exceeded 15500 U/ml. Neutralizing antibody titers against the XBB.1.16 and XBB.1.42 variants were higher in age- and sex-matched noninfected 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 COVID-19 vaccination with the bivalent mRNA vaccine (original and omicron BA.1), high S antibody titers correlated with disease prevention, even in the presence of XBB variants.