Introduction：A large rubella outbreak has been occurring in Tokyo, Japan since June 2012. Rubella vaccination, introduced in Japan in 1976, has targeted different age groups, resulting in a large proportion of the current population being unvaccinated.Methods：Rubella cases reported in Tokyo from 2 January 2012 to 21 April 2013 were analysed. A clinical case had generalized maculopapular rash, fever and lymphadenopathy; a laboratory-confirmed case was a clinical case with a positive serology or polymerase chain reaction test for rubella. A descriptive analysis of cases by age, sex, vaccination history and other epidemiological information was conducted.Results：A total of 2382 cases were reported from all areas of Tokyo. Three-quarters were male ( n = 1823; 76.5%); the highest number of cases occurred among males aged 35–39 years and females aged 20–24 years. About a third of males (27%) and females (32%) reported never receiving rubella vaccination, with 68% and 56%, respectively, having an unknown vaccination status.Discussion：This outbreak reflects the changing, yet incomplete, immunization policies for rubella in Japan that may increase the risk of congenital rubella syndrome (CRS). To suppress the outbreak of rubella and prevent CRS cases, we recommend vaccination for the entire susceptible population.

None.

Since late 2013 through March 2014, Japan experienced a rapid rise in measles cases. Here, we briefly report on the ongoing situation and share preliminarily findings, concerns and challenges and the public health actions needed over the coming months and years.

Measles is a notifiable disease in Japan based on nationwide case-based surveillance legally requiring physicians to report all clinically diagnosed and laboratory-confirmed cases within seven days, but preferably within 24 hours. After a large outbreak in 2007–2008 (more than 11 000 cases reported in 2008 alone) and a goal of elimination by April 2015, a catch-up programme using the bivalent measles-rubella (MR) vaccine was offered for grades seven and 12 (ages 12–13 and 17–18 years) from April 2008 through March 2013. During this period, there was an estimated 97% decline in measles notifications, and the cumulative number of reported cases has been steadily declining over the last five years (732 cases in 2009, 447 cases in 2010, 439 cases in 2011, 293 cases in 2012 and 232 cases in 2013). However, since late 2013 through March 2014, the country experienced a resurgence only a year after a large rubella outbreak.

Introduction: In Japan, syphilis notifications have increased. Men who have sex with men (MSM) in Tokyo have contributed substantially to the increase in syphilis notifications. We thus aimed to determine the correlates of incident syphilis among them. Methods: MSM who attended a Tokyo clinic that serves sexual minorities were recruited in a case-control study in 2015. A case was seropositive for primary/secondary/asymptomatic syphilis at enrolment visit and seronegative at prior visit or had oral ulcers positive for Treponema pallidum DNA at enrolment. For each case, two controls seronegative at enrolment and prior visit were selected. Using logistic regression, odds ratios (ORs) and 95% confidence intervals (CIs) were estimated to assess for correlates of case status. Results: Among 35 cases, the median age was 37 (range = 21–63) years and was similar to the 71 controls. Among HIV-positive participants (26 cases and 67 controls), cases were independently associated with higher frequency of anal or oral sex (OR = 3.4; 95% CI = 1.4–8.6; increase per category from < 1/month, ≥ 1/month but < 1/week, to ≥ 1/week) and no or inconsistent condom use during anal or oral sex (OR = 3.0; 95% CI = 1.1–8.3; increase per category from using every time, occasionally, to never), adjusted for residency and time between visits. Discussion Modifiable behaviours were associated with incident syphilis, and dissemination of prevention messages are needed.

Objective: Monitoring the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants is important due to concerns regarding infectivity, transmissibility, immune evasion and disease severity. We evaluated the temporal and regional replacement of previous SARS-CoV-2 variants by the emergent strains, Alpha and Delta. Methods: We obtained the results of polymerase chain reaction screening tests for variants conducted in multiple commercial laboratories. Assuming that all previous strains would be replaced by one variant, the new variant detection rate was estimated by fitting a logistic growth model. We estimated the transmission advantage of each new variant over the pre-existing virus strains. Results: The variant with the N501Y mutation was first identified in the Kinki region in early February 2021, and by early May, it had replaced more than 90% of the previous strains. The variant with the L452R mutation was first detected in the Kanto-Koshin region in mid-May, and by early August, it comprised more than 90% of the circulating strains. Compared with pre-existing strains, the variant with the N501Y mutation showed transmission advantages of 48.2% and 40.3% in the Kanto-Koshin and Kinki regions, respectively, while the variant with the L452R mutation showed transmission advantages of 60.1% and 71.9%, respectively. Discussion In Japan, Alpha and Delta variants displayed regional differences in the replacement timing and their relative transmission advantages. Our method is efficient in monitoring and estimating changes in the proportion of variant strains in a timely manner in each region.

Utilizing data presented in the article by Miyashita et al., we illustrate the importance of testing data when assessing surveillance data. Accounting for the number of tests (denominator) and positivity (proportion of tests positive for a specific pathogen(s)) improves data interpretation in ways not possible from numerator case data alone.