What causes latent TB?

Latent tuberculosis infection usually follows exposure to someone with active tuberculosis in the airways. The bacteria can remain inactive in the body, so a person with latent infection does not have the illness pattern of active TB and generally does not spread it to others. A positive screening result does not by itself show whether infection is latent or active. Symptoms, examination and sometimes chest imaging help clinicians make that distinction. Immune suppression can allow contained bacteria to become active later, which is why assessment matters even when a person feels well.

Arrange a clinical assessment after a positive result or a significant exposure. Tuberculosis Screening may involve a skin test or blood test, followed by checks for active disease when appropriate. Tell the clinician about previous TB, medicines, pregnancy, liver problems and conditions that affect immunity. If latent infection is confirmed, Antibiotic Treatment may be offered to reduce the chance of future active disease. Take any prescribed course exactly as directed and report new symptoms or troublesome reactions rather than stopping medicines without advice.

Seek prompt medical care for a persistent cough, coughing blood, chest pain, fever, night sweats, unusual tiredness or unexplained weight loss after exposure or a positive test. These symptoms need assessment for active TB or another illness. Seek urgent help for severe breathing difficulty, confusion or coughing a large amount of blood.

Which tests will distinguish latent infection from active TB? How might my other medicines or health conditions affect treatment? What symptoms should prompt immediate review?