Tuberculosis: First Symptoms, How It Spreads and Diagnosis

Tuberculosis is often thought of as a disease of the past, yet it remains one of the most widespread deadly infections in the world. The good news: caught early, TB is curable. The bad news: it hides for a long time behind ordinary tiredness and a lingering cough, and a person may be ill for months without knowing, infecting those around them. Here are the first symptoms, how TB spreads and how it is diagnosed.

What Tuberculosis Is and How You Catch It

The cause of TB is a mycobacterium (Koch's bacillus). Infection is airborne: a person with the open form releases bacteria into the air when coughing. An important point: very many people are infected, but only about 5–10% fall ill — in the rest, immunity keeps the bacterium in a "dormant" (latent) state. Latent infection is not contagious and has no symptoms, but it can reactivate when immunity drops.

First Symptoms of Tuberculosis

The insidious thing about TB is its gradual, subtle onset. Classic first signs: a cough lasting more than 3 weeks (dry or productive), weakness and persistent fatigue, unexplained weight loss, night sweats, a prolonged low-grade fever (37–37.5 °C) and loss of appetite. Later there may be blood in the sputum and shortness of breath. A lingering cough with weight loss is a reason to get checked urgently.

How TB Spreads and Who Is at Risk

TB spreads through the air from a person with the active (open) form. Risk is higher with close prolonged contact, weakened immunity, HIV infection (see HIV and AIDS), diabetes, undernutrition and smoking. A single contact on public transport is usually not dangerous — prolonged time together indoors matters more.

Open and Closed Forms: Why the Open Form Is Dangerous

In the open (bacteria-shedding) form the person is contagious — bacteria are present in the sputum. In the closed form there is no shedding and the person is not contagious. Latent infection is not a disease at all but symptom-free carriage. Only a doctor can determine the form and contagiousness from test results.

Diagnosis: Chest X-ray and Skin Tests

The main screening in adults is an annual chest X-ray. In children skin tests are used — they show contact with the mycobacterium. A positive test is not a diagnosis of TB but a reason for follow-up with a specialist.

Tests and Confirming the Diagnosis

The diagnosis is confirmed by sputum testing (microscopy, culture, PCR for the mycobacterium) and a chest CT. A complete blood count may show non-specific changes — a raised ESR, shifts in white cells — but on their own they do not confirm TB. If you have confusing results, you can upload them for decoding.

Treatment and Why You Must Not Stop

TB is treated with several drugs over a long course — usually at least 6 months. The key rule: do not stop treatment when you feel better — undertreated TB comes back and becomes drug-resistant (a dangerous form). Treatment is led by a specialist; self-treatment is unacceptable.

Prevention and the BCG Vaccine

Children are given the BCG vaccine — it protects infants from the most severe forms of TB. For adults, prevention means an annual chest X-ray, not smoking, and treating latent infection in risk groups. After contact with someone with the open form, get checked.

When to See a Doctor

Do not delay for a cough lasting more than 3 weeks, especially with weight loss, night sweats, a prolonged fever or blood in the sputum. These signs call for ruling out TB. If you are unsure where to start, you can describe your symptoms — the service suggests which checks to discuss with a doctor.

This article is for informational purposes only and does not replace a doctor's consultation. TB is diagnosed and treated by a specialist.