Research Library

Effectiveness of Canada’s tuberculosis surveillance strategy in identifying immigrants at risk of developing and transmitting tuberculosis: a population-based retrospective cohort study

Abstract

In Canada, tuberculosis disproportionately affects people who were born abroad. The national tuberculosis medical surveillance programme aims to prevent these cases. These people are referred (referrals) for further in-country surveillance after migration if they have a history of active tuberculosis or have features of old, healed tuberculosis on chest radiograph. Others who are not referred (non-referrals) do not undergo surveillance. In this study we looked at the risk of transmitting TB that comes from referrals and non-referrals. We also compared the transmission rates between the two groups. To make this comparison, we looked at information that Alberta Tuberculosis Registry had about foreign-born migrants (aged 15-64 years). We looked at information about people who came to Alberta between Jan 1, 2002, and Dec 31, 2013. We were interested in cases that had culture-positive pulmonary tuberculosis. We found that the incidence of culture-positive pulmonary disease was nine times higher in referrals than all non-referrals and five times higher in referrals than non-referrals from high-risk countries. Despite a much higher incidence of pulmonary tuberculosis in referrals than non-referrals, referrals were 80% less likely to transmit tuberculosis. But we suggest that instead of focusing only on referrals, Canada could consider screening and treatment of latent tuberculosis in all migrants from high-risk countries.