The 2011 measles outbreak in Tokyo. An analysis of surveillance data.

OBJECTIVES: The study was conducted with the intention of establishing a strategy to eliminate measles on the basis of an analysis of the epidemiological profile of measles cases reported in Tokyo during the year 2011. METHODS: We investigated measles cases reported to the Tokyo Metropolitan Government in 2011, recorded as part of the National Epidemiological Surveillance of Infectious Diseases. Factors analyzed included age, vaccination status for each patient, cases for which records were discarded after laboratory confirmation, genotype of the measles virus and relationships between dates of specimen collection and results of polymerase chain reaction (PCR) and IgM antibody tests. RESULTS: A total of 178 measles cases were reported in Tokyo during 2011, and the majority of cases (128, 71.9%) were reported during the peak period from epiweeks 13 to 24. The largest age group reported was one to four years of age (40, 22.5%) followed by groups of 20-29 and 30-39 years of age (both 34, 19.1%). Most cases were sporadic, with only six outbreaks occurring. Even then, the numbers of cases for each outbreak was less than five. More than half of the patients in all age groups, except for the 1-4-year-old group, had not been vaccinated or did not have a record of vaccination. Genotypes D4 and D9 of measles virus were detected in most cases. However, genotype D5, which had been circulating in Japan before 2008, was not detected. CONCLUSION: Imported viruses were the cause of measles cases reported in Tokyo during 2011. The disease control was better than that in 2007 and 2008 because of the swift and appropriate responses to the occurrences. It is also possible that there has been an increase in the proportion of people with immunity to measles. Increasing the rate of immunization, performing effective surveillance, and confirming suspicious measles cases by using molecular methods are important for achieving the elimination of measles.

Diarrhea as a minor adverse effect due to oral polio vaccine.

Using the adverse events monitoring system of Japan, we observed diarrhea cases in approximately 10% of patients who received oral poliovirus vaccine (OPV). This study was conducted to investigate whether diarrhea among children aged 0 to 1 is caused by OPV or by other factors such contact at the doctor's office and/or with others outside the home. We conducted a survey of the health of children after regular health check-ups and after the administration of the OPV. The data from the health check-ups were used as a control for the OPV case group. We compared the first-OPV dose vaccination group as well as the second-OPV dose vaccination group to the health check-up group. For cases of diarrhea, the odds ratio of the OPV group to the health check-up group was 1.776. Our findings strongly suggest that post-OPV cases of mild diarrhea are closely related to the administration of the OPV.

Shedding of Rubella Virus among Infants with Congenital Rubella Syndrome Born in Tokyo, Japan, 2013-2014.

Rubella is usually a mild illness, with febrile rash being its main symptom. However, serious consequences of rubella infection can result when the infection occurs during the early stages of pregnancy. After the occurrence of a rubella outbreak in Japan that was observed from 2012 to 2013, 45 infants were reportedly born with congenital rubella syndrome (CRS). We prospectively followed the 15 CRS cases reported in Tokyo to determine the virus shedding periods by using nested reverse transcriptase-polymerase chain reaction to detect rubella virus genes. Throast swabs were used for virus detection. The virus shedding period was measured from birth until the time when the sample last tested positive followed by 2 consecutive negative samples. Kaplan-Meier method was used to estimate the proportion of cases remaining positive for rubella virus genes over time. The proportion of CRS cases shedding virus dropped steadily after birth, dropping to 33.8% at 6 months and 16.9% at 12 months. Our findings also suggested that the earlier the mother's onset of rubella during pregnancy, the longer the infant remained positive. Based on our findings, we believe that infants with CRS should be monitored for rubella virus shedding until 1 year of age.