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IDWRMeasles update in Japan as of end of week 21 (28 May2008)

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


Epidemiological Information:


Between 1 January and 28 May 2008, a total of 8 415 cases were reported from all of 47 prefectures. The number of reported cases has been decreasing since 17th epidemiological week. Weekly reported cases in 21st epidemiological week dropped by 37% from the previous week, resulting in a total of 236 cases between 19 May and 25 May 2008.
Figure 1 shows the cumulative number of reported cases by each prefecture. A total of 1,169 cases were reported in Hokkaido, north most prefecture, as of 28 May, 2008. Of which, 521(44.4%) cases were from Sapporo city. The highest number of cases has been reported from Kanagawa, second populated prefecture neighboring Tokyo, with a total of 3,083.

Approximately 65% (5,447) of all reported cases were clinically-diagnosed cases and 35% (2,968) cases were laboratory confirmed cases (Fig. 2).  

Most affected age group was between 15 and 19 (2,071, 24.6 %), followed by between 10 and 14 (1,550, 18.4 %), and between 0 and 4 (1,150, 13.7%) (Fig. 3). Nearly 90% of the total cases were under the age of 30.  
The percentage of unvaccinated cases was 46.5%(3,910), while the cases with one-dose vaccination and two-dose vaccination account for 23.9% (2,013) and 0.8% (70), respectively. Twenty-nine percent (2,422) reported that their vaccine status were unknown (Fig. 4).

Five cases with encephalitis, aged from teenager to 40’s, were reported as of 21st week in 2008. All but one case were unvaccinated. A case in her 40’s stated her vaccination status was unknown. Regarding cases with pneumonia, children aged one or younger constitute 43.3 % (Fig. 5). In 2008, no fatal case had been officially reported as of 28 May.

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 May 2008, 16 PHIs reported 113 measles virus isolation/detection. Genotype D5 is detected in 75 of 81 viruses genotyped, genotype H1 in 4 (from domestic cases) and genotype A in 2 (from vaccinees within two weeks after vaccination).(see http://idsc.nih.go.jp/iasr/measles-e.html).

Public Health measures:

Japanese government set a goal in 2008 to eliminate measles by 2012. A nationwide effort to educate people on measles has been made; how severe the disease is, how to prevent from being infected with the virus. The government launched supplemental immunization 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 Measles-Rubella combined vaccine (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).

Important Note:

Given that Japan is hosting G8 Hokkaido Toyako Summit from 7 July to 9 July 2008 at Toyako Town located near Sapporo city, all visitors including foreigners should be advised to be vaccinated against measles before their arrival to Hokkaido, if they are susceptible.




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(2008/6/6 IDSC)
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