[Case-surveillance of measles in Aichi Prefecture in 2007]

Under the Japanese Infectious Disease Prevention Law, measles was monitored by the national epidemiological surveillance system through reports from sentinel clinical institutions until December 2007. In order to obtain rapid and precise information on measles outbreaks and take necessary actions, a case-surveillance system was introduced in Aichi Prefecture in February 2007. In this report, measles cases reported through the case-surveillance system were examined for characteristics of infection and the utility of the system.

The case-surveillance system for measles started in Aichi in February 2007, all local medical institutions being requested to provide a set of information on every measles case immediately after the clinical diagnosis was made. Reported data were processed by ourselves and real-time surveillance results were shown in our web site. Data were analyzed and compared with measles data from the national epidemiological surveillance system, reported by the sentinel clinical institutions in Aichi.

A total of 212 cases were registered through the case-surveillance from February to December 2007, including 123 (58.0%) adult cases (over 15 years old of age). In contrast, only 56 cases were registered in Aichi by the national epidemiological surveillance in 2007 including 11 adult cases (19.6%), indicating considerable under-representation of adult measles cases by the sentinel survey. Of the case-surveillance cases, 56 (26.4%) had an immunization history, 88 (41.5%) were without a history, and 68 (32.1%) were unknown, indicating that primary and/or secondary vaccine failure occurred in at least 26.4%.

The results of the case-surveillance of measles in Aichi provided useful information on characteristics of measles infection and proved to be effective in detecting the occurrence of measles rapidly and accurately. In order to achieve the Japanese target of measles elimination by 2012, it will be necessary to further strengthen the monitoring system and measures to contain spread of the disease.