How can latent tuberculosis become active many years after infection?

Latent tuberculosis occurs when the body’s immune system successfully sequesters the Mycobacterium tuberculosis bacteria within hard, nodular tubercles, preventing the disease from becoming active or contagious.1

The bacteria are hardy and can remain dormant inside these tubercles for many years—sometimes 40 years or more—while the host remains asymptomatic. The transition from a latent state to active pulmonary tuberculosis occurs when these original tubercles break down. This process releases viable bacilli into the bloodstream, allowing them to spread and create new tissue infections, most commonly in the upper portions of the lungs.12

This reactivation is often associated with factors that compromise the immune system, such as AIDS, aging, or other conditions that diminish the body's ability to maintain the containment of the bacteria. Once the infection becomes active, it is highly infectious and requires prompt medical intervention with antibiotic therapy to prevent further spread to other organs.13