Canada has one of the world's lowest rates of tuberculosis infection, but that doesn't mean the disease poses no threat here. TB represents a growing problem in prisons and among Canadians of native and Asian descent. Patients with active TB can be misdiagnosed because few physicians ever see the disease and because the bacillus can infect organs other than the lungs. Frequent screening of at-risk populations and a rigorous course of antibiotics for those who are infected are recommended.