Active TB Disease and Latent TB Infection

A person who is exposed to TB may not necessarily develop the disease. Most people are able to fight the infection using various components of their immune system. In fact, healthy people who are infected with TB only have a 10% chance of converting to active disease over their lifetime. Some are able to control the infection, but unable to completely remove it from their bodies. In these cases, the infection remains, lying in an inactive or “latent” state. This is often described as Latent TB Infection or LTBI. LTBI may develop into active disease someday, often when the persons immune system becomes weakened.

People with latent TB infection do not show any signs of TB disease so it can go unnoticed. Since this latent infection can become active at any time and then spread to other individuals it is usually treated with antibiotics.

People with active TB disease do have signs and symptoms.   These symptoms of active TB disease are easy to confuse with those of many other diseases. This chart details the main differences between active TB disease and latent TB infection.

Active TB Disease

Latent TB Infection

Can be spread to others Yes, through droplets in the air No, Mycobacteria are not expelled
Chest x-ray Abnormal findings; will show signs of damage Abnormal findingsrarely seen
Sputum Test (SSM) Test may be positive Test will be negative
Antibiotic treatment Yes, to treat active disease Yes, to prevent conversion to active disease