Tuberculosis: 3. Epidemiology

An 8-year-old grade 3 student comes to her family physician’s office with her mother because the school has asked that she be tested for tuberculo-sis. The testing will be done at the school, but the mother wants to know if it is really necessary. The child is well and has no symptoms of tuberculo-sis. She was born in the Philippines, and the family immigrated to Canada 2 years previously. Despite efforts to control tuberculosis (TB), this disease remains a majorworld health problem. In 1990 there were 7.5 million new cases and 2.5million deaths.1 An estimated 1 billion people worldwide are infected with the causative organism, making this the most common human infection known. In Canada approximately 2000 new cases and more than 100 deaths are reported each year.2 The number of Canadians who are asymptomatically in-fected with the tubercle bacillus is unknown. Since the turn of the 19th century, when as many as 1 in 5 Canadians had TB in their lifetime, the combination of an improved standard of living, public health interventions to interrupt transmission, and effective treatment have re-duced morbidity and mortality rates and have made the elimination of TB a pos