Tuberculosis, Lung Health and Respiratory Diseases

Latent TB Infection and Active TB Disease

Persons with latent TB infection do not feel sick and do not have any symptoms. They are infected with M. tuberculosis, but do not have TB disease. The only sign of TB infection is a positive reaction to the tuberculin skin test or TB blood test. Persons with latent TB infection are not infectious and cannot spread TB infection to others

The TB bacteria overcome the defenses of the immune system and begin to multiply, resulting in the progression from latent TB infection to Active TB disease. Some people develop TB disease soon after infection, while others develop TB disease later when their immune system becomes weak.