Read condition-specific symptoms and clinical context for Mycobacterium tuberculosis. The bacterium behind TB. Active disease differs from latent infection.
M. tuberculosis is a slow-growing bacterium that causes tuberculosis (TB). Disease usually affects the lungs, but can involve other organs. TB in the lungs can spread through the air. Infection and disease are different: inactive infection causes no TB symptoms and is not contagious. Active disease may cause illness, although symptoms can be mild or absent. Symptoms alone cannot establish a diagnosis; testing and clinical assessment are needed.
Possible symptoms when active TB affects the lungs. Symptoms at other body sites differ.
Possible symptoms: Cough lasting three weeks or longer; Chest pain; Coughing up blood or sputum; Fatigue; Weight loss; Fever or night sweats.
CDC advises contacting a healthcare provider or local health department about TB testing if you have symptoms of active TB.
Latent TB infection does not cause symptoms of TB disease. An absence of symptoms does not exclude infection.
Latent infection can be present without symptoms.
Latent infection can develop into active disease. Testing and clinical assessment establish the diagnosis.
Source check: 2026-09-16. Educational content; independent scientific review remains pending.