School contact tracing following a cluster of tuberculosis cases in two Scarborough schools

Ten refugee children from an extended family were diagnosed with active tuberculosis. The family had recently arrived in Scarborough from Somalia. Mantoux skin testing was organized by the local health department for students in the two schools the children attended. An eleventh active case was found on screening. The reactivity rate for children tested once was 1.2% for Canadian-born students, and 14.6% for foreign-born students. Reactivity rates of students tested once were not significantly higher than those in comparison schools. Repeat skin testing of non-reactors revealed a conversion rate of 4.4%. This rate may be an overestimate as a result of the booster phenomenon. Increased risk of testing positive was associated with a history of BCG and being foreign-born in all schools. As rates of tuberculin reactivity have greatly increased in Scarborough schools since the early 1980s, it is recommended that health departments screen foreign-born students for tuberculosis upon entrance to school.