There are three reasons for the persistence of tuberculosis despite the war that rages against it in Canada and the rest of the world. The first is drug-resistance. The drugs that are used to combat TB are antibiotics, which become useless if they are not used properly. Because bacteria are living things, they are constantly adapting to resist the drugs used to treat them. When new strains develop that are not killed by these drugs, they proliferate despite the drug treatment, and are only killed when new drugs are found. Multi-drugs resistance is beginning to be a problem in Canada, as new strains of the disease are entering the country.
One third of the World Population is infected with tuberculosis.
The second reason for the continued persistence of TB in Canada is that people from countries where TB is more common are immigrating into Canada. Particularly in the developing World, where drug treatments for TB are not always readily available as they are here, TB has continued to be a major menace to society. One of the costs of our support of immigration into Canada from these countries is that we must carefully watch the TB levels in the incoming population. Canadian immigration laws currently require that all immigrants over the age of ten be screened for active tuberculosis, and that all positive cases be followed-up once entering Canada. Still, 63% of TB cases in Canada are among the foreign-born.
Thirdly, TB continues to infect Canadians because there exists a reservoir for the disease among population groups considered "high risk". Individuals at high risk for tuberculosis fit into one of two groups: first are those whose immune system is compromised, such as patients with HIV; and second are those located in socio-depressed areas, which may include inner-city slums, reservations, or underdeveloped countries.