Transmission In Japan Research Articles

Group B Streptococcal Disease in Infants in Japan.

This review describes the epidemiology of group B Streptococcus (GBS) infection in infants in Japan and discusses unresolved issues and future perspectives. Guidelines for the prevention of vertical transmission in Japan were implemented in 2008. The incidence of early-onset disease in Japan has remained stable at approximately 0.10/1000 livebirths or less, which is lower than in Europe and North America. The incidence of late-onset disease is also low, but has increased over the last decade, with an estimated 0.29/1000 livebirths in 2020. National surveillance studies in 2011-2015 and 2016-2020 reported case fatality rates of 4.5% and 6.5% for early-onset disease and 4.4% and 3.0% for late-onset disease, respectively. Sequelae of neurodevelopmental impairments were considerably associated with infants who developed meningitis. Predominant neonatal invasive strains have remained in the following order of serotypes: III, Ia, Ib and V, for the past 30 years. Conversely, the predominant serotypes of maternal colonization strains markedly changed from serotypes VI and VIII around 2000 to serotypes Ia, Ib, III and V over the last decade. Recurrence rates among infants < 1-year-old were estimated to be 2.8%-3.7%, and preterm birth and antenatal maternal GBS colonization were risk factors for recurrence. Several unresolved issues remain. First, the exact disease burden remains unclear because Japan does not have a nationwide system to register all infants affected by invasive GBS disease, and even population-based surveys are limited to up to 10 of the 47 prefectures. Others include low adherence to prevention guidelines of vertical transmission and the development of strategies based on Japanese epidemiological evidence rather than the Center for Disease Control and Prevention guidelines. The effectiveness of introducing maternal vaccines in Japan, where the disease incidence is low, needs to be carefully verified.

Measures for the Prevention of Mother-to-Child Human T-Cell Leukemia Virus Type 1 Transmission in Japan: The Burdens of HTLV-1-Infected Mothers.

The main mode of mother-to-child transmission of the human T-cell leukemia virus (HTLV)-1 is through breastfeeding. Although the most reliable nutritional regimen to prevent HTLV-1 transmission is exclusive formula feeding, a recent meta-analysis revealed that short-term breastfeeding within 90 days does not increase the risk of infection. The protocol of the Japanese Health, Labor, and Welfare Science Research Group primarily recommended exclusive formula feeding for mothers who are positive for HTLV-1. However, there has been no quantitative research on the difficulties experienced by HTLV-1-positive mothers in carrying out these nutritional regimens, including the psychological burden. Therefore, this review was performed to clarify the burdens and difficulties encountered by mothers who are positive for HTLV-1; to this end, we analyzed the data registrants on the HTLV-1 career registration website "Carri-net" website. The data strongly suggest that it is not sufficient to simply recommend exclusive formula feeding or short-term breastfeeding as a means of preventing mother-to-child transmission; it is important for health care providers to understand that these nutritional regimens represent a major burden for pregnant women who are positive for HTLV-1 and to provide close support to ensure these women's health.

Effect of COVID-19 vaccination on household transmission of SARS-CoV-2 in the Omicron era: The Vaccine Effectiveness, Networking, and Universal Safety (VENUS) study

ObjectivesTo evaluate the effectiveness of vaccination on reducing household transmission of SARS-CoV-2 among common household types in Japan during the Omicron variant wave. MethodsThis retrospective study was conducted using vaccination records, COVID-19 infection data, and resident registry data from two Japanese municipalities. Households that experienced their first COVID-19 case between January and April 2022 were categorized into two groups according to the presence/absence of children aged ≤11 years. We constructed multivariable logistic regression models with generalized estimating equations to calculate the odds ratios (ORs) and 95% confidence intervals for household transmission according to the vaccination statuses of primary cases and household contacts. ResultsWe analyzed 7326 households with 17,586 contacts. In all households, the OR for household transmission was <0.6 (P <0.001) when the primary case and/or contact were vaccinated. In households with children aged ≤11 years, the OR was 0.71 (P <0.001) when only the contact was vaccinated. In households with all members aged ≥12 years, the OR was <0.5 (P <0.001) when the primary case and/or contact were vaccinated. ConclusionCOVID-19 vaccination effectively reduced household transmission in Japan during the Omicron variant wave.

Awareness of Infectious Disease Screening During Early Pregnancy and Knowledge About its Vertical Transmission in Japan: A Report from the Pregnant Women Health Initiative

ObjectivesWe aimed to clarify the accuracy of pregnant women’s knowledge and understanding regarding infectious disease screening in early pregnancy and clarify the roles that should be played by health care providers in promoting the health of pregnant women and their children.MethodsA cross-sectional questionnaire survey was conducted in 25 hospitals across Japan from May 2018 to September 2019. We compared the agreement rates regarding screening results for hepatitis B virus (HBV), hepatitis C virus (HCV), syphilis, human T-cell leukemia virus-1 (HTLV-1), and cervical cytology in the medical records and understanding of their results by pregnant women. We then investigated whether participants had knowledge regarding the risk of mother-to child transmission in these diseases and factors associated with their knowledge.ResultsWe enrolled 2,838 respondents in this study. The rates of agreement for HBV and cervical cancer screening related to human papillomavirus infection were “substantial,” those for syphilis was “moderate,” and those for HCV and HTLV-1 were “fair,” according to the Kappa coefficient. The rate of knowledge regarding mother-to-child transmission of syphilis was highest (37.0%); this rate for the other items was approximately 30%. Increased knowledge was associated with higher educational level and higher annual income.Conclusions for PracticePregnant women in Japan had generally good levels of understanding regarding their results in early-pregnancy infectious disease screening. However, they had insufficient knowledge regarding mother-to-child transmission of these diseases. Health care providers should raise awareness in infectious disease prevention among pregnant women and the general public, providing appropriate measures and implementing effective perinatal checkups and follow-ups for infectious diseases.

Do house prices play a role in unconventional monetary policy transmission in Japan?

This study comprehensively analyzes the role of house prices in the transmission mechanism of unconventional monetary policy (UMP) in Japan using structural vector autoregression models. The empirical results show that house prices are significantly affected by UMP shocks, and fluctuations in house prices considerably affect macroeconomic variables. With a set of robustness checks and extensions, the findings indicate that house prices provide important channels for UMP transmission.

Impact of the Coming-of-Age Day and ceremony on the risk of SARS-CoV-2 transmission in Japan: A natural-experimental study based on national surveillance data.

BackgroundQuantifying the impact on COVID‐19 transmission from a single event has been difficult due to the virus transmission dynamics, such as lag from exposure to reported infection, non‐linearity arising from the person‐to‐person transmission, and the modifying effects of non‐pharmaceutical interventions over time. To address these issues, we aimed to estimate the COVID‐19 transmission risk of social events focusing on the Japanese Coming‐of‐Age Day and Coming‐of‐Age ceremony in which “new adults” practice risky behavior on that particular day.MethodsUsing national surveillance data in Japan in 2021 and 2022, we conducted difference‐in‐differences regression against COVID‐19 incidences by setting “new adults” cases as the treatment group and the cases 1 year younger or older than these “new adults” as the control group. In addition, we employed a triple differences approach to estimate the risk of holding the Coming‐Age ceremony by using a binary variable regarding the presence or absence of the ceremony in each municipality.ResultsWe estimated the relative risks (RRs) of the Coming‐of‐Age Day as 1.27 (95% confidence interval [CI] 1.02–1.57) in 2021 and 3.22 (95% CI 2.68–3.86) in 2022. The RR of the Coming‐of‐Age ceremony was also large, estimated as 2.83 (1.81–4.43) in 2022.ConclusionsWhen planning large social events, it is important to be aware of the unique risks associated with these gatherings, along with effective public health messages to best communicate these risks.

Aedes albopictus Strain and Dengue Virus Serotype in the Dengue Fever Outbreaks in Japan: Implications of Wolbachia Infection.

From August 27 to October 15, 2014, a dengue fever outbreak with 158 autochthonous cases occurred after nearly 70 years of no reports of autochthonous cases in Japan. The most competent mosquito vector for dengue virus (DENV) transmission in Japan is Aedes albopictus. Since A. albopictus is widely distributed throughout Japan, we examined the susceptibility of this species to infection by DENV and the relationship of the endosymbiont Wolbachia (wAlbA and wAlbB) with susceptibility to DENV. The A. albopictus YYG strain, collected from the Yoyogi Park in 2014, the epicenter of the dengue fever outbreak, was found to have lower susceptibility to DENV 1 and 3 than that of the indigenous Japanese strains A. albopictus EBN 201808 (F1 from the field) and A. albopictus ISG 201603. Furthermore, the A. albopictus EBN 201808 strain showed the same susceptibility to DENV3 as the A. albopictus ISG 201603tet strain (Wolbachia-free). Susceptibility to DENV3 was not related to Wolbachia strains wAlbA or wAlbB in the A. albopictus ISG 201603 strain.

Effectiveness of mRNA COVID-19 Vaccines in Japan during the Nationwide Pandemic of the Delta Variant.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remained a major global health concern in 2021. To suppress the spread of infection, mass vaccinations have been performed across countries worldwide. In Japan, vaccinations of the first and second doses for most of the nation were performed during the nationwide outbreak of the B.1.617.2 (Delta) variant with the L452R spike protein mutation, and the effectiveness of the vaccinations to suppress the spread of COVID-19 among the people in Japan remains uncertain. In this study, adults aged ≥18 years, who were in contact with patients with COVID-19 and underwent nasopharyngeal swab reverse transcription-polymerase chain reaction (RT-PCR) tests during August and September 2021 at a mass screening test center in Japan, were enrolled. In this period, more than 95% of the COVID-19 infections were reportedly caused by the Delta variant. As a result, a total of 784 adults with recent contact history, including 231 (29.5%) RT-PCR test-positive cases, were enrolled. The test positivity rate was lower in individuals who had been vaccinated twice than in unvaccinated individuals (12.5% vs. 39.0%, p < 0.0001), with the risk ratio of 0.32 (95% confidence interval 0.23-0.46). The vaccine effectiveness was the highest between 7-90 days after the second vaccine dose. In conclusion, two doses of mRNA COVID-19 vaccines effectively suppressed transmission in Japan during the nationwide pandemic of the Delta variant, estimated to have prevented 50-80% of the infection.

Long-term dynamics of Norovirus transmission in Japan, 2005-2019.

Norovirus continues to evolve, adjusting its pathogenesis and transmissibility. In the present study, we systematically collected datasets on Norovirus outbreaks in Japan from 2005 to 2019 and analyzed time-dependent changes in the asymptomatic ratio, the probability of virus detection, and the probability of infection given exposure. Reports of 1,728 outbreaks were published, and feces from all involved individuals, including those with asymptomatic infection, were tested for virus in 434 outbreaks. We found that the outbreak size did not markedly change over this period, but the variance in outbreak size increased during the winter (November–April). Assuming that natural history parameters did not vary over time, the asymptomatic ratio, the probability of virus detection, and the probability of infection given exposure were estimated to be 18.6%, 63.3% and 84.5%, respectively. However, a model with time-varying natural history parameters yielded better goodness-of-fit and suggested that the asymptomatic ratio varied by year. The asymptomatic ratio was as high as 25.8% for outbreaks caused by genotype GII.4 noroviruses. We conclude that Norovirus transmissibility has not changed markedly since 2005, and that yearly variation in the asymptomatic ratio could potentially be explained by the circulating dominant genotype.

Nation-Wide Viral Sequence Analysis of HIV-1 Subtype B Epidemic in 2003-2012 Revealed a Contribution of Men Who Have Sex With Men to the Transmission Cluster Formation and Growth in Japan.

Background: To better understand the epidemiology of human immunodeficiency virus type 1 (HIV-1) subtype B transmission in Japan, phylodynamic analysis of viral pol sequences was conducted on individuals newly diagnosed as HIV-1 seropositive.Methodology: A total of 5,018 patients newly diagnosed with HIV-1 infection and registered in the Japanese Drug Resistance HIV Surveillance Network from 2003 to 2012 were enrolled in the analysis. Using the protease-reverse transcriptase nucleotide sequences, their subtypes were determined, and phylogenetic relationships among subtype B sequences were inferred using three different methods: distance-matrix, maximum likelihood, and Bayesian Markov chain Monte Carlo. Domestically spread transmission clusters (dTCs) were identified based on the following criteria: >95% in interior branch test, >95% in Bayesian posterior probability and <10% in depth-first searches for sub-tree partitions. The association between dTC affiliation and individuals' demographics was analyzed using univariate and multivariate analyses.Results: Among the cases enrolled in the analysis, 4,398 (87.6%) were classified as subtype B. Many of them were Japanese men who had sex with men (MSM), and 3,708 (84.3%) belonged to any of 312 dTCs. Among these dTCs, 243 (77.9%) were small clusters with <10 individuals, and the largest cluster consisted of 256 individuals. Most dTCs had median time of the most recent common ancestor between 1995 and 2005, suggesting that subtype B infection was spread among MSMs in the second half of the 1990s. Interestingly, many dTCs occurred within geographical regions. Comparing with singleton cases, TCs included more MSM, young person, and individuals with high CD4+ T-cell count at the first consultation. Furthermore, dTC size was significantly correlated with gender, age, transmission risks, recent diagnosis and relative population size of the region mainly distributed.Conclusions: Our study clarified that major key population of HIV-1 subtype B epidemic in Japan is local MSM groups. The study suggests that HIV-1 subtype B spread via episodic introductions into the local MSM groups, some of the viruses spread to multiple regions. Many cases in dTC were diagnosed during the early phase of infection, suggesting their awareness to HIV risks.

The Effectiveness of Unconventional Monetary Policy in Japan

:Since the global financial crisis of 2007–2008, central bankers around the world have been forced to abandon conventional monetary policy tools in favor of unconventional policies such as quantitative easing, forward guidance, and even lowering the interest rate paid on bank reserves into negative territory. Japan, which faced a crisis in its banking sector and came up against the theoretical zero lower bound on interest rates nearly a decade earlier, was a pioneer in the use of many of these unconventional policy tools. This article analyzes the effectiveness of Japan’s bold experiment with unconventional monetary policy. Using a panel of bi-annual bank data covering the full universe of Japanese commercial banks over a fifteen-year period, this study analyzes the effectiveness of quantitative easing policy on the bank lending channel of monetary policy transmission. Our findings suggest that Japan’s unconventional monetary policy worked: there is a bank lending channel of monetary policy transmission in Japan. These results are robust to the inclusion of time fixed effects and generalized method of moments analysis.

Genetic diversity of Phytophthora nicotianae reveals pathogen transmission mode in Japan

Phytophthora nicotianae is an important soil-borne pathogen in tropical, subtropical and temperate regions. To clarify the genetic diversity of P. nicotianae and to understand its mode of transmission in Japan, we developed six new microsatellites markers, consisting of six loci and 39 alleles. In a phylogenetic analysis, 138 isolates, including 125 from Japan and 13 from overseas, were shown to differ, even though some were collected from the same host and location, suggesting that there is no geographic or host plant clustering. Population structure analysis also revealed a highly admixed population of P. nicotianae in Japan. Molecular analysis suggested high variance between individuals but no significant differences between populations. Both A1 and A2 mating types were present in the same population, which could be due to high levels of variance between individuals in the population. The absence of geographical structure between populations also suggests that the pathogen is able to migrate from one population to another. We propose that this phenomenon could result from human activities related to the transport of plant and associated agricultural materials.

Estimating the annual risk of tuberculosis infection in Japan from interferon-gamma release assay data

To assess tuberculosis transmission frequency at a population level, the age-dependent Mantoux test has been used widely to estimate the annual risk of infection (ARI) with Mycobacterium tuberculosis. However, the widespread Bacille Calmette-Guerin (BCG) immunization program implemented in Japan in the 20th century has made natural infections with M. tuberculosis difficult to distinguish from immune responses against this vaccine. Consequently, a recognized alternative method for measuring the frequency of primary infections, the interferon-gamma release assay (IGRA), which partially decays as a function of time after infection, is used. We aimed to estimate the ARI in Japan from IGRA data along with its response decay information using mathematical modeling. Devising a partial differential equation system, we computed the probability of IGRA positivity as a function of time and age, accounting for the time-varying force of infection and decay function of the IGRA response. Jointly estimating the force of infection and the parameters governing the decay function of the IGRA response, we found that the age-dependent increasing pattern of the IGRA response was captured by the proposed simple model, yielding estimates of the time-dependent force of infection. ARI decreased as a function of time in the study subjects for all geographic locations. By the year 2030, our model showed that the median age of infection is predicted to be delayed by 40–50 years compared with that in 1940. The geographic variations in the ARI were striking, ranging from under 0.1% to 0.6% in 2018, which echoes the longstanding notion of highly heterogeneous geographical tuberculosis transmission in Japan.

An ascovirus isolated from Spodoptera litura (Noctuidae: Lepidoptera) transmitted by the generalist endoparasitoid Meteorus pulchricornis (Braconidae: Hymenoptera).

The family Ascoviridae is a recently described virus family whose members are transmitted by parasitoids and cause chronic and lethal infections in lepidopteran insects. Little is known about the biology and ecology of ascoviruses, and few isolates have been found outside the United States. We report here the isolation of a new ascovirus variant from Spodoptera litura in Japan. Full genome sequence and phylogenetic analyses showed that this virus was closely related to variants in Heliothis virescens ascovirus-3a, and it was named HvAV-3j. HvAV-3j has a DNA genome of 191 718 bp, with 189 putative ORFs and a GC content of 45.6 %, and is highly similar to HvAV-3h, which was isolated in China. In a field survey, the endoparasitoid Meteorus pulchricornis caused a high percentage of parasitization in populations of S. litura larvae, and under laboratory conditions M. pulchricornis was able to transmit HvAV-3j from infected to uninfected larvae by oviposition. Meteorus pulchricornis is thus likely to be a major vector for HvAV-3j transmission in Japan. This species is recognized here for the first time as a vector of ascoviruses that parasitizes a range of host species that extends across families.

The transmissibility of noroviruses: Statistical modeling of outbreak events with known route of transmission in Japan.

In Japan, the fraction of norovirus outbreaks attributable to human-to-human transmission has increased with time, and the timing of the increased fraction has coincided with the increase in the observed fraction of genogroup II genotype 4 (GII.4). The present study aimed to estimate the time-dependent changes in the transmissibility of noroviruses. The effective reproduction number (Ry), for year y, was estimated by analyzing the time series surveillance data for outbreak events from 2000 to 2016. Ry was estimated by using the fraction of outbreak events that were attributable to human-to-human transmission and by employing three different statistical models that are considered to mechanistically capture the possible data-generating process in different ways. The Ry estimates ranged from 0.14 to 4.15 in value, revealing an overall increasing trend (p<0.05 for all three models). The proportion of outbreaks caused by GII and GII.4 viruses among the total events also increased with time, and positive correlations were identified between transmissibility and these proportions. Parametric modeling of Ry indicated that the time-dependent patterns of Ry were better described by a step function plus linear trend rather than the step function alone that reflects the widespread use of reverse transcriptase PCR (RT-PCR) in and after 2007 for laboratory diagnosis. Accordingly, we conclude that norovirus transmissibility has increased over the past 16 years in Japan. The change is at least partially explained by the time-dependent domination of the contagious GII genogroup (e.g., GII.4), indicating that noroviruses better fitted to humans have selectively caused the human-to-human transmissions, thereby altering the epidemiology of this pathogen.

Susceptibility of Aedes flavopictus miyarai and Aedes galloisi mosquito species in Japan to dengue type 2 virus

ObjectiveTo evaluate the potential of local mosquitoes to act as vectors for dengue transmission in Japan. MethodsSerotype 2 ThNH28/93 was used to test the dengue susceptibility profiles of Aedes flavopictus miyarai (Ae. f. miyarai), Aedes galloisi (Ae. galloisi) and Aedes albopictus (Ae. albopictus), which were collected in Japan. We used Aedes aegypti from Thailand as a positive control. The mosquitoes were infected with the virus intrathoracically or orally. At 10 or 14 days post infection, the mosquitoes were dissected and total RNA was extracted from their abdomens, thoraxes, heads and legs. Mosquito susceptibility to dengue virus was evaluated using RT-PCR with dengue virus-specific primers. Differences in the infection and mortality rates of the different mosquito species were tested using Fisher's exact probability test. ResultsThe infection rates for dengue virus administered intrathoracically to Ae. f. miyarai, Ae. galloisi and Aedes aegypti mosquitoes were identical by RT-PCR on Day 10 post infection. All of the body parts we tested were RT-PCR-positive for dengue virus. For the orally administered virus, the infection rates in the different body parts of the Ae. f. miyarai mosquitoes were slightly higher than those of Ae. albopictus mosquitoes, but were similar to the control mosquitoes (P > 0.05). The mortality rates for Ae. f. miyarai and Ae. albopictus mosquitoes were similar (P = 0.19). Our data indicated that dengue virus was able to replicate and disseminate to secondary infection sites in all of the four mosquito species (Japanese and Thai). ConclusionsAe. albopictus is a well-known candidate for dengue transmission in Japan. However, our data suggest that Ae. f. miyarai from Ishigaki Island (near Okinawa Island) and Ae. galloisi from Hokkaido (Northern Japan) should also be regarded as potential vectors for dengue transmission in these regions. Further studies on these mosquitoes should be conducted.

Analysis of influenza transmission in the households of primary and junior high school students during the 2012-13 influenza season in Odate, Japan.

BackgroundHouseholds are one of the major settings of influenza transmission in the community and transmission is frequently initiated by school-aged children. We surveyed households with primary school (PS) and/ or junior high school (JH) children for the 2012–13 influenza season in Odate, Japan then characterized the epidemiology of influenza household transmission as well as estimated the serial intervals.MethodsWe delivered a self-reported questionnaire survey to households with PS and/or JH school children in Odate City, Japan. Influenza A (H3N2) virus predominantly circulated during the 2012–13 influenza season. We investigated the epidemiological characteristics of within-household transmission and calculated the serial intervals (SI). SIs were drew by a non-parametric model and compared with parametric models by the Akaike Information Criterion. The covariable contributions were investigated by the accelerated failure model.ResultsHousehold influenza transmission was identified in 255 out of 363 household respondents. Primary school (PS) children accounted for 45.1 % of primary cases, and disease transmission was most commonly observed between PS children and parents, followed by transmission from PS children to siblings. In primary cases of PS or JH children, younger age and longer absence from school were significantly associated with household transmission events. The mean SI was estimated as 2.8 days (95 % confidence interval 2.6-3.0 days) in the lognormal model. The estimated acceleration factors revealed that while secondary school age and the absence duration > 7 days were associated with shorter and longer SIs, respectively, antiviral prescriptions for primary cases made no contribution.ConclusionsHigh frequencies of household transmission from primary school with shorter SI were found. These findings contribute to the development of future mitigation strategies against influenza transmission in Japan.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-015-1007-8) contains supplementary material, which is available to authorized users.

Prevalence of human T-cell leukemia virus type 1 carrier in Japanese pregnant women in 2013.

Since September 2010, in Japan serological screening for the detection of human T-cell leukemia virus type 1 (HTLV-1) antibodies can be performed for all women during pregnancy with the Japanese public funds for strategies for prevention of HTLV-1 vertical transmission, because Japan, especially Kyushu area, has been reported to be one of the areas of highest prevalence of HTLV-1 in the world [1, 2]. In our previous study [3], we examined the prevalence of HTLV-1 carrier in Japanese pregnant women according to the implement rate and results of HTLV-1 screening and confirmation tests of women who gave births in Japan in 2011. The total rates of positive HTLV-1 screening tests and positive western blot (WB) test in positive screening tests were 0.32% and 49.8%, respectively in 2011. Considering the response rate and the rate of implementation of WB test, the number of HTLV-1 carrier in Japanese pregnant women in 2011 was estimated to be 1,560 (0.15%). In addition, although the number of delivery in Kyushu area was only 14% of Japanese deliveries, 53% of HTLV-1 carrier of Japanese pregnant women was present in Kyushu area. Recently, the migration of Japanese people from Kyushu area to the metropolitan areas has been thought to contribute to a significant decrease of HTLV-1 carriers in Kyushu area and an increase in Kanto (including Tokyo) area in Japan [1, 4]. To confirm this migration in Japanese pregnant women, on December 2014, we requested again 2,544 obstetrical facilities that are members of Japan Association of Obstetricians and Gynecologists (JAOG) to provide information of HTLV-1 tests in pregnant women who delivered at ≥ 22 weeks’ gestation in 2013. A total of 1,356 (53.3%) of 2,544 obstetrical facilities responded and information on a total of 538,167 women, accounting for approximately 54% of all deliveries that occurred in Japan during the study period (approximately 1,001,800 births) was provided. In 2013, the total rates of positive HTLV-1 screening tests and positive WB test in positive screening tests were 0.35% and 50.8%, respectively. Considering the response rate and the rate of implementation of WB test, the number of HTLV-1 carrier in Japanese pregnant women in 2013 was estimated to be 1,780 (0.18%). Table 1 shows the difference in the estimated number of HTLV-1 carrier based on positive WB test by area in Japan between 2011 and 2013. The estimated number of HTLV-1 carrier in 2013 seemed to be more than that in 2011, especially in the northeast and southwest (Kyushu) areas. In addition, 51% of HTLV-1 carrier of Japanese pregnant women was present in Kyushu area, although the number of delivery in Kyushu area was only 13% of Japanese deliveries in 2013. Although the migration of Japanese people from Kyushu area to the metropolitan areas has been supposed to contribute to a significant decrease of HTLV-1 carriers in Kyushu area, the estimated number of HTLV-1 carrier of pregnant women seemed to be increased in Kyushu area. In addition, the estimated rate of HTLV-1 carrier in pregnant women in Kyushu area was still significantly higher than that in the other areas (P < 0.01 by the Chi-square test). Therefore, there are still remaining problems concerning the locality for strategies for prevention of HTLV-1 vertical transmission in Japan.

Retrospective search for dengue vector mosquito Aedes albopictus in areas visited by a German traveler who contracted dengue in Japan

A German traveler developed dengue fever in late August 2013, following a direct flight from Germany. Autochthonous dengue virus (DENV) infection has not been reported in Japan. To evaluate the risk of autochthonous DENV transmission in Japan, the authors performed a retrospective search of the five areas visited by the German patient to determine the population density of dengue vector mosquito, Aedes albopictus. The annual mean temperature of each area was higher than 12°C, which is considered suitable for the establishment of A. albopictus populations. Our retrospective search revealed the population density of A. albopictus to be high in the urban areas of Japan.

Effect of non-stationary climate on infectious gastroenteritis transmission in Japan.

Local weather factors are widely considered to influence the transmission of infectious gastroenteritis. Few studies, however, have examined the non-stationary relationships between global climatic factors and transmission of infectious gastroenteritis. We analyzed monthly data for cases of infectious gastroenteritis in Fukuoka, Japan from 2000 to 2012 using cross-wavelet coherency analysis to assess the pattern of associations between indices for the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Infectious gastroenteritis cases were non-stationary and significantly associated with the IOD and ENSO (Multivariate ENSO Index [MEI], Niño 1 + 2, Niño 3, Niño 4, and Niño 3.4) for a period of approximately 1 to 2 years. This association was non-stationary and appeared to have a major influence on the synchrony of infectious gastroenteritis transmission. Our results suggest that non-stationary patterns of association between global climate factors and incidence of infectious gastroenteritis should be considered when developing early warning systems for epidemics of infectious gastroenteritis.