Infectious Disease Sureillance Center

IDWRMeasles update in Japan as of week 21 (from 21 to 27 May 2007)

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

Sentinel Surveillance:

Between 1 January and 27 May 2007, a total of 1121 measles cases from 3000 pediatric sentinels have been reported nationwide. 657 cases of them (58.6%) were reported from southern Kanto area including Saitama, Tokyo and Chiba. Age distribution is characteristic; fewer cases are seen among 0 to 4-years old (N=426, 38.0%) compared to average year (55 to 67%) and more cases are reported from 10 to 14-years-old (N=358, 31.9%) compared to average year (5 to 15%).

In 21st epidemiological week (from 21 to 27 May), 215 new cases from pediatric sentinels have been reported from 27 prefectures in Japan; 108 cases from southern Kanto area, 35 cases from northern part of Japan including Miyagi and Hokkaido. This was the highest number of cases reported per week in 2007.

Regarding adult measles (cases of 15-year-old and older), between 1 January and 27 May 2007, a total of 387 cases have been reported from 450 hospital sentinels; 139 cases from Tokyo, 45 cases from Kanagawa, 40 cases from Miyagi and 34 cases from Saitama. The numbers of reported adults’ cases were also highest since the surveillance system started in 1999 Cases reported from southern Kanto area are increasing continuously. This report also indicates that the outbreak is spreading to northern part of Japan.

From the result of hospital sentinels, 33.3% (N=129)of cases are among 20 to 24-year-old, 23.3% (N=90) are among 25 to 29-year-old, and 21.4% (N=83) are among 15 to 19-year-old. Roughly 91% (N=352)) of them were reported from the group under 35-years-old.

School closure:

According to the Ministry of Health, Labor and Welfare, between 1 April and 26 May 2007, a total of 103 schools were closed completely (78) or partially (25) due to measles outbreak. 64 of them were high schools (33) or colleges/ universities (31). Approximately 70% of them were reported from Kanto area including Tokyo.

Severity of the epidemic:

Three cases of encephalitis related to measles have been reported in 2007; one in the teens and the others in the twenties.

Virus isolated:

According to the local public health laboratories, all of the sequenced measles viruses (N=21) have been identified as D5 strain.

Public Health measures:

  • Information regarding the recent situation of measles epidemic has been rapidly provided to the public.
  • Public sensitization has been conducted regarding the importance of the vaccination, especially to the people who are at highest risk (those who have had neither measles infection nor vaccination in the past). Routine vaccination, especially the first dose, was enhanced.
  • As of 16 May 2007, 37 out of 131 local governments nationwide reported that they have started notifiable surveillance system for measles cases.
  • 500 000 doses of measles-containing vaccine and 600 000 diagnostic kits will additionally be supplied to healthcare facilities and diagnostic laboratories by the end of June 2007.

(2007/6/8 IDSC)

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