Tuberculosis

Tuberculosis, or TB, is an infectious disease caused by bacteria called Mycobacterium tuberculosis. It usually affects the lungs, but it can also affect other parts of the body such as the lymph nodes, bones, kidneys, or brain.

TB exists in two forms. In latent TB, the bacteria stay in the body in an inactive state; the person has no symptoms, feels well, and cannot pass it on, but the infection could become active later. In active TB, the bacteria are multiplying and causing illness, and a person with active TB in the lungs or throat can spread it to others. TB is a major global health concern, but with the right treatment it is preventable and curable.

Active TB in the lungs typically causes a cough that lasts more than three weeks, which may bring up phlegm or blood. Other common symptoms include a high temperature, drenching night sweats, extreme tiredness, loss of appetite, and unexplained weight loss.

If TB affects other parts of the body, symptoms depend on the area involved, such as swollen lymph nodes, joint or bone pain, or, if it reaches the brain, headaches, a stiff neck, and confusion. See a doctor if you have a cough lasting more than three weeks or other ongoing symptoms, especially if you cough up blood.

TB spreads through the air. When a person with active TB in the lungs or airways coughs, sneezes, or speaks, they can release tiny droplets containing the bacteria, which others may breathe in. Spread usually requires prolonged, close contact, such as living in the same household, rather than brief everyday contact.

Some people are more at risk of catching TB or of latent TB becoming active. This includes people with a weakened immune system, such as those living with HIV or taking medicines that suppress immunity, young children, people who are in close contact with someone who has active TB, and people who live in or have travelled from areas where TB is more common.

For suspected active TB in the lungs, doctors usually start with a chest X-ray and laboratory tests on samples of phlegm to look for the bacteria. Samples may also be grown in the laboratory (a culture) to confirm TB and to check which antibiotics will work, although this can take several weeks. If TB is suspected elsewhere in the body, a sample of fluid or tissue may be taken.

To check for latent TB, which has no symptoms, a Mantoux skin test or a blood test (an interferon-gamma release assay) can be used. These tests show whether the immune system has reacted to TB bacteria, which helps decide whether treatment is needed to prevent active disease later.

Active TB is treated with a combination of antibiotics taken for at least six months. A common approach uses several medicines together for the first two months, then fewer for the remaining months. Most people start to feel better within a few weeks, but it is essential to take every dose and complete the full course, even after symptoms improve.

Stopping treatment early, or taking it irregularly, is dangerous because it can allow the bacteria to survive and become resistant to the antibiotics, which is much harder to treat. For this reason, treatment is closely supervised, and support may be offered to help people complete it. Latent TB may also be treated with antibiotics to prevent it becoming active, particularly in people at higher risk.

The BCG vaccine offers some protection and is offered to people at higher risk, such as infants in areas where TB is more common and some healthcare workers. Diagnosing and fully treating active cases, and treating latent TB in people at risk, are key to stopping TB from spreading. People with active lung TB may be advised to take precautions, such as covering coughs and limiting close contact, until they are no longer infectious.

With a complete course of the right antibiotics, most people with TB are cured. Because TB is an infectious disease with public-health importance, cases are usually reported to health authorities so that close contacts can be checked and offered testing if needed.