Measles elimination in Canada.

To describe the progress and challenges in achieving measles elimination in Canada, we analyzed national data on measles cases for 1998-2001. To assess the status of measles elimination in Canada, we estimated the effective reproductive number, R. Measles elimination was defined as the interruption of endemic transmission and failure to reestablish endemic transmission after importation. Twelve isolated cases, 29 cases (72.4% were linked to 2 outbreaks), 199 cases (96.9% were linked to 4 outbreaks of 2, 6, 30, and 155 cases), and 34 cases (73.5% were linked to 8 outbreaks of 2, 2, 2, 2, 3, 3, 3, and 8 cases) were reported in 1998, 1999, 2000, and 2001, respectively. R ranged from 0.58 to 0.95. Multiple chains of transmission occurred in religious communities that actively oppose or resist immunization efforts. Epidemiological and virological evidence suggests that endemic transmission of measles has been mostly interrupted since 1998.