Epidemiological features and surveillance performance of measles in the Republic of Korea, 2002-2011.

Measles was declared eliminated from the Republic of Korea in 2006; however, recently the number of reported cases has been gradually increasing. To address this issue, we summarized the measles surveillance data collected during 2002-2011, and aimed to evaluate the performance of the current surveillance system in Korea. We analyzed data from the national surveillance system to describe the occurrence of measles. Surveillance indicators proposed by the World Health Organization were used to evaluate the performance of the current measles surveillance system. Between 2002 and 2005, a gradual decrease in confirmed cases of measles was noted, whereas cyclical increases were noted from 2006 to 2011. Since 2006, confirmed cases of measles were more likely to be identified by laboratory methods. In general, the incidence of confirmed case was less than one per million in Korea; however, this figure increased in 2002 (1.3/million), 2007 (4.0), and 2010 (2.3). Most cases were occurred in the age groups 0-23 months and 12-17 years. Laboratory testing was performed in most suspected cases; however, the proportion of discarded cases was low. Overall, more than half of the reported cases experienced an onset of symptoms from April to June. The incidence of measles is relatively low in Korea, and the laboratory surveillance may have helped in identifying under-diagnosed cases within the country. It remains important to continuously assess the surveillance data to improve the surveillance performance.