Tuberculosis

What is it?

According to WHO: tuberculosis is an infectious disease caused by bacteria that mostly affect the lungs, and it spreads through the air when an infected person coughs, sneezes or spits. According to the CDC it is caused by Mycobacterium tuberculosis bacteria, and usually affects the lungs but can also affect the brain, kidneys or spine. MedlinePlus adds that the disease can be treated with antibiotics and is fatal if not treated.

The difference between latent infection and active disease according to the CDC: in latent infection a small amount of bacteria is alive but inactive, there are no symptoms and the person does not spread the infection; in TB disease there is a large amount of active bacteria, the person feels ill and may pass them to contacts. The CDC states that a person with latent infection may develop active disease at any time if not treated. This page does not cover further details of the mechanisms of progression from latent to active.

WHO figures: in 2024, 10.7 million people worldwide fell ill with TB (5.8 million men, 3.7 million women and 1.2 million children), and 1.23 million people died (including 150,000 people living with HIV). About a quarter of the world's population carries TB bacteria without symptoms, and only 5 to 10% of them develop active disease. The CDC estimates that about 13 million people in the United States have latent infection and that one in 10 without treatment will develop active disease.

Causes

Mycobacterium tuberculosis bacteria (CDC). They spread in small airborne particles 1 to 5 microns in diameter produced when a person with pulmonary or laryngeal TB coughs, speaks or sings, and they stay in the air for hours depending on the environment, and poorly ventilated enclosed spaces carry a higher risk than outdoors (CDC). According to the NHS: the disease spreads when a person breathes in these droplets regularly and for a long time, and latent infection does not spread to others.

Risk factors

According to WHO: diabetes, HIV, weakened immunity, malnutrition, smoking and alcohol use increase susceptibility to TB disease. WHO estimates the number of cases attributable in 2024 at about 0.97 million to malnutrition, 0.93 million to diabetes, 0.74 million to alcohol, 0.70 million to smoking and 0.57 million to HIV. People living with HIV are 12 times more likely to develop the disease according to WHO.

According to the CDC: the risk of exposure is higher for people born in countries where TB is common or who have travelled to them, those living in congregate settings (shelters, prisons), those who have recently been in contact with someone with active disease, and those who work in hospitals and care homes. The risk of progressing to disease is higher in people with AIDS, diabetes, cancer or weakened immunity, children under 5 years, recent infection, and silicosis. MedlinePlus and the NHS add older people, people who received inadequate earlier TB treatment, and people exposed to immunosuppressants after organ transplant or steroids.

Symptoms

Latent infection has no symptoms (CDC). As for active TB in the lungs, the CDC lists its symptoms: cough lasting 3 weeks or more, chest pain, coughing up blood or phlegm, weakness and tiredness, weight loss, loss of appetite, chills, fever, night sweats. WHO states that symptoms may be mild for months, allowing the infection to spread without knowledge.

When TB affects areas outside the lungs, symptoms appear according to the organ affected, such as spinal pain, blood in the urine, or headache and confusion in meningitis (CDC). The NHS mentions swollen glands, body aches, joint swelling, abdominal pain and neurological symptoms.

How is it diagnosed?

Two initial tests according to the CDC: the blood test (IGRA), which measures the immune response to TB proteins and is not affected by the BCG vaccine, and the skin test (Mantoux), in which the provider injects a substance under the skin and the result is read after 2 to 3 days. A positive result means TB bacteria are in the body but does not distinguish latent from active, so a chest X-ray and sputum test are needed. The test result usually stays positive even after treatment, so keeping a record of it is advised.

According to WHO: rapid diagnostic tests (point-of-care tests and molecular tests) are recommended as the initial test, and give preliminary results within 48 hours to guide treatment. MedlinePlus states that confirming active disease requires sputum samples, a chest X-ray or a tissue sample depending on the site of infection. This page does not cover the details of test specifications.

Treatment

The treatment categories usually used are listed here; this is not a prescription. The doctor chooses the plan according to each person's condition; do not change any medicine or dose without a specialist.

According to the CDC: both latent and active TB can be treated with medicines, and the medicines must be taken and completed exactly as the provider recommends, because skipping doses or stopping early is dangerous. WHO stresses that stopping early may cause antibiotic resistance.

The medicine categories mentioned (chosen with the doctor): for latent infection isoniazid, rifampin and rifapentine in different combinations; for active disease combinations including ethambutol, isoniazid, moxifloxacin, rifampin, rifapentine and pyrazinamide (CDC), and WHO lists the first-line medicines: rifampicin, isoniazid, pyrazinamide and ethambutol. The sources state that treatment lasts months (the CDC mentions 3 to 9 months for latent and 4 to 9 months for active depending on the regimen), and the doctor determines the duration.

The CDC recommends directly observed therapy (DOT) as the best way to ensure adherence, with a health worker observing the person take the medicine in person or remotely. Drug-resistant TB needs a complex and long treatment that may last months or years and must be managed by a TB expert, according to the CDC; WHO states that TB resistant to rifampicin and isoniazid is multidrug-resistant. The CDC warns of serious side effects that call for immediate medical attention: liver injury (abdominal pain, nausea and jaundice), dizziness, loss of appetite, flu-like symptoms, and numbness or tingling in the limbs.

Prevention

According to WHO: the BCG vaccine prevents deaths and protects children from severe forms of the disease, TB preventive treatment (TPT) prevents infection from turning into disease, and early detection of symptoms, contact tracing and infection control in health facilities also help. The CDC states that treating latent infection protects against developing active disease. The NHS notes that the BCG vaccine is given in the United Kingdom to defined groups; this page does not cover vaccination policies in other countries, so consult the health authority in your country.

Living with it

According to MedlinePlus: active TB can mostly be cured with antibiotics, but can be fatal if not treated. Completing the medicines protects against relapse and drug resistance (NHS and CDC). WHO states that only about 2 in 5 people with drug-resistant TB received treatment in 2024.

Common questions