Outbreak of measles in a religious group--Montreal, Quebec.

Between 1 May and 3 September, 1994, 44 cases of measles were reported to the public health authorities of the Health and Social Services Board for the Montreal Centre Region. Distribution of cases by week of onset is shown in Figure 1. Thirty-nine of those cases met the national case definition for measles and almost half (n=19) were serologically confirmed by the detection of immunoglobulin M (IgM). Since the beginning of the year, the observed incidence of measles in this region has been 3.4 cases per 100,000 person years. The overall incidence of confirmed cases in the Montreal area exceeds the total (2.4 per 100,000 person years) for all other regions in Quebec combined. The last major measles epidemic in Quebec occurred in 1989.