Active case-based surveillance for measles in China: lessons learned from Shandong and Henan provinces.

To identify issues relevant to nationwide implementation, a project was conducted during 1999-2001 to support and evaluate the development of a case-based measles surveillance system (MSS) in Shandong and Henan provinces, China. The performance of MSS surveillance and the descriptive characteristics of reported measles cases and outbreaks were analyzed. Of the 5782 suspected cases in 2001, 85% were investigated and 66% had serologic results. In all, 39% of cases were confirmed, 36% were compatible, and 25% were discarded; 81% of outbreaks identified involved <15 cases. In all, 15% of cases were temporary (floating) residents. The MSS was useful in monitoring the impact of measles control activities. Standardized laboratory quality-assurance activities and indicators should be developed while the system is still in the early stages of implementation.