Tuberculosis: transmission, prevention and key facts

Essentials

Bacterial infection that most often affects the lungs and is transmitted to the air during close contact.

Agent: Mycobacterium tuberculosis
Transmission or exposure: Respiratory

Situation and vulnerability

Repeated exposure in poorly ventilated space and weakened immunity may increase the risk.

Signs and limits of their interpretation

Prolonged cough, fever, night sweats or weight loss can lead to the search for tuberculosis. These signs are not specific. The disease may affect organs other than the lungs, with different manifestations.

Diagnosis and monitoring

Infection tests alone do not demonstrate an active disease. The assessment may involve clinical examination, imaging and microbiological research on suitable samples. The search for resistance helps to choose the treatment when the disease is confirmed.

Check these benchmarks in the WHO reference →

Prevention and care

Contact testing and appropriate treatment complement ventilation and protection in the care settings.

Practical issues

Does a positive infection test mean I'm contagious?

No. Additional examinations are needed to search for active disease. Diagnosis and treatment are the responsibility of a medical team.

Is a disease-free TB infection the same as contagious pulmonary tuberculosis?

No. Infection and active disease are distinct. The medical team evaluates the situation and the necessary measures.

Preparing for an exchange with a professional

Cough duration and general development
Known contact with a case and previous reviews
Treatments, vulnerabilities and history of tuberculosis

Bring the full minutes and dates. This information facilitates evaluation; its collection must not delay an urgent appeal.

Individual decisionThe choice of a test, treatment or prevention depends on the local situation and recommendations. In case of distress, call 911.

Biologiste travaillant au microscope dans un laboratoire. AI-generated illustration. — **Studying bacteria** — Biologist working under microscope in a laboratory.
Image generated by artificial intelligence. Fictive scene; no particular bacteria are represented.

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Related fact sheets

These sheets share ways or contexts of exhibition in our catalogue. This reconciliation does not establish a differential diagnosis.

Compare Tuberculosis with Associated Files →

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In practiceObserve and understand

Tuberculosis: latent infection and active disease

A positive immune-based test does not establish contagious TB. Clinical assessment distinguishes infection without disease from active disease and checks for lung or laryngeal involvement.

Real electron micrograph of Mycobacterium tuberculosis, digitally colorized — **Mycobacterium tuberculosis: a real observation, with added colors.** CDC / Ray Butler, MS ; Janice Haney Carr, 2006. Public domain. Free source, credits and terms: CDC PHIL. A laboratory image cannot interpret personal exposure or establish a diagnosis.

Tuberculosis: latent infection and active disease — explanations and limits
Report item	What it helps explain	Question to ask
Latent infection	It does not spread to others. Preventive treatment can reduce progression to disease.	Has active disease been ruled out before preventive treatment?
Active pulmonary or laryngeal disease	It can spread through shared air. Protection advice and contact investigations depend on public health assessment.	Who coordinates contact follow-up and return to activities?

References for these explanations

CDC · Active tuberculosis ↗

Sources consulted on 14/10/2026. Examples and diagrams are educational; the original guidance defines its scope.