Infectious Disease Sureillance Center

IDWRMeasles update in Japan as of end of week 12 (23 March 2008)

Infectious Disease Surveillance Center, National Institute of Infectious Diseases, Tokyo, Japan

Epidemiological Information:
Between 1 January and 23 March 2008, a total of 4,648 cases were reported from 45 out of 47 prefectures. Tokyo metropolitan region (Kanagawa, Tokyo, Chiba, and Saitama), Hokkaido in northern Japan, and Fukuoka in western Japan have been the three largest epidemic areas during this period. Figure 1 shows the cumulative number of reported cases by each prefecture. Among these cases, 3,030 cases (65.2%) were clinically-diagnosed cases and 1,618 cases (34.8%) were laboratory confirmed cases (Fig. 2). Most affected age group was between 15 and 19 (1,139, 24.5%), followed by between 10 and 14 (892, 19.2%), and between 20 and 24 (638, 13.7%) (Fig. 3). These age groups accounted for more than 50%, and nearly 90% of the total cases were under the age of 30. The percentage of unvaccinated cases was 47.6% (2,213), while the cases with one-dose vaccination and two-dose vaccination account for 23.6% (1,096) and 0.8% (38), respectively. Twenty-eight percent (1,301) reported that their vaccine status were unknown (Fig. 4). Four cases with encephalitis, aged from 16 and 38 years, were reported as of 12th week. All of them were unvaccinated. Regarding cases with pneumonia, children aged one or younger constitute 44.3% (Fig. 5). No fatal case had been officially reported as of 23 March, 2008.

In Japan, prefectural and municipal public health institutes (PHIs) report the results of isolation/detection of infectious agents from specimens collected by 1) sentinel clinics and hospitals under the National Epidemiological Surveillance of Infectious Diseases (NESID), 2) other medical institutions and 3) health centers. From January to March 2008, 13 PHIs reported 80 measles virus isolation/detection. Of these, 51 of 52 strains genotyped were identified as D5 (see

Public Health Measures:
At national and local level, public sensitization was strengthened in terms of the necessity of vaccinating children and young adults at high risk using measles-containing vaccine. Some local governments such as cities of Yokosuka and Yokohama both in Kanagawa prefecture neighboring Tokyo have implemented mass immunization campaign mostly using Measles-Rubella combined vaccine (MR vaccine) targeting at children and teenagers. It was reported that Odate city, Akita in northern Japan have successfully contained outbreak through emergency vaccine campaign for measles. Contact tracing has been conducted in Okinawa prefecture, a south most prefecture in Japan.

Japanese government launched supplemental vaccine campaign on 1 April 2008, which targets age-cohorts of both 13 years of age and 18 years of age for the next five years, in addition to the current two age-cohorts of 1 years of age and one year prior to entering to elementary school, mostly using MR vaccine. The government will collect the information on vaccine coverage of the new targeted age-cohorts, based on both demography from local government and school registry from schools in cooperation with Ministry of Education, Culture, Sports, Science and Technology (MEXT).

Figure 1 Figure 2 Figure 3
Figure 4 Figure 5

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