Tuberculosis (TB) is one of the most common infections in the world. About 2 billion people are infected with TB and nearly 3 million people are killed by it each year. In Canada, there are about 1,600 new cases of TB every year.
The bacterium that causes TB is called Mycobacterium tuberculosis. Someone can become infected and yet not have any symptoms of the active disease – this is called inactive TB.
For someone with a healthy immune system, there's only a 10% lifetime chance of the TB bacteria reactivating and causing the active symptoms of TB. If the immune system has been weakened because of HIV (human immunodeficiency virus) or other illnesses, the risk of moving from an inactive infection to an active symptomatic disease increases to 10% per year.
Babies, preschool children, and seniors are also at greater risk of reactivation due to weaker immune systems.