Latent vs Active TB
| Feature | Latent TB | Active TB |
|---|---|---|
| Symptoms | None | Cough >3 weeks, weight loss, night sweats, fever, coughing blood |
| Contagious | No | Yes (pulmonary TB) |
| Chest X-ray | Usually normal | Often shows abnormalities |
| Treatment | 3-6 months (fewer drugs) | 6+ months (multiple drugs, at least 4 initially) |
| Risk of progression to active TB | 5-10% lifetime risk without treatment | Already active disease |
Latent TB Screening Tests
| Test | How It Works |
|---|---|
| IGRA (Interferon Gamma Release Assay) | Blood test measuring immune response to TB proteins — more specific, not affected by BCG vaccination |
| Mantoux (tuberculin skin test) | Skin injection, read at 48-72 hours; can give false positives if previously BCG vaccinated |
Treatment Regimens
| TB Type | Standard Treatment |
|---|---|
| Active TB (drug-sensitive) | Rifampicin, isoniazid, pyrazinamide, ethambutol for 2 months, then rifampicin + isoniazid for 4 more months |
| Latent TB | Isoniazid + rifampicin for 3 months, or isoniazid alone for 6-9 months |
| Drug-resistant TB | Longer, more complex regimens with specialist input — 9-20+ months |
Active TB Requires Isolation and NotificationActive pulmonary TB is a notifiable disease requiring public health follow-up and contact tracing. Patients with infectious TB need to isolate (usually at home) until deemed non-infectious, typically after 2 weeks of effective treatment.
Treatment Completion Is CriticalStopping TB treatment early is the main cause of drug-resistant TB developing — a much harder-to-treat and more dangerous form of the disease. Directly observed therapy (DOT) programmes help ensure patients complete their full treatment course.
Does the BCG vaccine prevent TB completely?
BCG provides good protection against severe childhood TB (especially TB meningitis) but offers variable, often limited protection against adult pulmonary TB — it doesn't guarantee complete immunity.
Can TB affect organs other than the lungs?
Yes — extrapulmonary TB can affect lymph nodes, bones, kidneys, and the brain (TB meningitis), among other sites. These forms are generally not contagious to others.
Who should be screened for latent TB?
People with close contact with active TB cases, those from high-TB-prevalence countries, healthcare workers, and people who are immunocompromised (including before starting biologic medications) are commonly screened.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.