What is tuberculosis?


What is tuberculosis?

What is tuberculosis?

Tuberculosis is a disease caused by a bacterium that mainly affects the lungs to cause a persistent and, occasionally bloody, cough.

What is tuberculosis?

What is tuberculosis?

  • Tuberculosis is an infection caused by the bacterium Mycobacterium tuberculosis.
  • Tuberculosis mainly affects the lungs but can spread to other parts of the body, such as the bones and nervous system.
  • It can also cause meningitis and inflammation of the membranes surrounding the brain and spinal cord.
  • Most healthy people with a fully functioning immune system will be able to kill the Mycobacterium tuberculosis bacteria before it causes symptoms.
  • In a small proportion of people, the infection will progress to active disease.
  • If left untreated, this active disease will kill around half of these patients.
  • Individuals with a weakened immune system, for example people with HIV, are particularly prone to developing active disease.
  • Around one third of the world’s population are believed to be infected with Mycobacterium tuberculosis and more than two million people die from tuberculosis each year.
  • There are two types of tuberculosis infections, latent and active.

Latent tuberculosis infections

  • People with latent infection do not have any signs or symptoms of the disease.
  • They are not infectious and cannot spread the infection to anyone else.
  • However, the infection can reactivate after many years of latency.
  • Reactivation is more likely in people whose immune system is weakened, for example if they have HIV or are on immunosuppressant drugs.

Active tuberculosis infections

  • People with active tuberculosis experience symptoms of the tuberculosis.
  • They can spread the infection to others.


  • Tuberculosis is spread through the inhalation of tiny droplets from the coughs or sneezes of an infected person with an active infection.
  • Infection usually only spreads after prolonged exposure to someone with the illness.
  • Tuberculosis will, therefore, often spread within a family or group of people living in the same house.


  • When tuberculosis affects the lungs it causes a persistent, and occasionally bloody, cough.
  • More generally, it causes symptoms such as weight loss, high temperature, night sweats, fatigue and loss of appetite.
  • Tuberculosis only causes symptoms in the active stage of the infection and even then symptoms can vary from person to person.


  • Tuberculosis can be cured if infected individuals are given the proper treatment, usually a six-month course of antibiotics.
  • Several different antibiotics are used to treat tuberculosis as some forms of the infection are resistant to certain antibiotics.
  • Treatment time can be doubled or even tripled if you are infected with an antibiotic-resistant form of tuberculosis.
  • Before 1910, tuberculosis was a serious health problem in the UK. Levels of the disease started to decrease from 1910 due to improvements in living conditions and the availability of better drug treatments.
  • In the last 20 years cases of tuberculosis have started to rise again in the UK. This is partly because of reactivation of latent infections in people from countries where tuberculosis is more common.
  • Combating the global burden of tuberculosis will rely on improvements in drug therapy, early detection of drug resistance and the development of better vaccines.


  • The Bacillus Calmette-Guerin (BCG) vaccine helps protect against tuberculosis.
  • Although it is no longer part of the NHS childhood vaccination schedule, if a child has an increased risk of being exposed to tuberculosis they will be given the vaccine.
  • The vaccine is 70 to 80 per cent effective against the most severe forms of tuberculosis, such as tuberculosis meningitis. It is less effective against respiratory forms of the disease.

The Bacillus Calmette-Guerin (BCG) vaccine helps protect against tuberculosis.
Image credit: Shutterstock

This page was last updated on 2021-07-21

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