Tuberculosis is an ancient disease that primarily affects the lungs. It is still a leading cause of death in many parts of the world.


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Biology, Health


Tuberculosis Screening

Three women examine an x-ray as they screen patients for tuberculosis in London, England.

Photograph by the Ministry of Information Photo Division Photographer
Three women examine an x-ray as they screen patients for tuberculosis in London, England.

Tuberculosis (TB) is an ancient disease that affected Neolithic humans, ancient Egyptians, and ancient Greeks, and still has widespread impacts. Until the early 20th century, TB was a leading cause of death in Europe and North America. At the time, those who were infected were isolated in sanitariums, places where the sick were sent to rest and recover. The development of antibiotics in the 1940s meant that TB could be treated more effectively.

Tuberculosis is caused by bacteria known as Mycobacterium tuberculosis. The disease is characterized by the damage it causes to the lungs. Those infected with tuberculosis cough up blood and mucus, and they experience weight loss, lack of appetite, fever, fatigue, and night sweats. This serious condition has the potential to be fatal, and it is one of the leading causes of death globally.

Upon infection, tuberculosis bacteria spread within the lungs and form nodules that break down respiratory tissues, creating holes in the lungs. The bacteria also breaks down blood vessels, causing blood to be coughed up. Although TB is most well-known for its effects on the lungs, the disease can impact other organs, such as the kidneys, spine, and brain.

A person who is infected with TB can spread the bacteria through the air when they cough or sneeze. Some people may carry the disease without showing any symptoms and without being contagious—this is known as a latent TB infection. A quarter of the people living with TB worldwide have a latent infection.

TB is endemic to certain regions of the world, such as Africa, Russia, Eastern Europe, Asia, Latin America, and the Caribbean. It is these areas where one is most likely to contract the disease. Developing countries have much higher rates of TB than developed nations. Children in developed nations are often vaccinated with the bacillus Calmette-Guerin (BCG) vaccine. However, this vaccine is not effective in adults.

Certain factors, such as tobacco and drug use, increase the risk of contracting TB. Working or living around those at higher risk of TB also increases potential exposure to the bacteria. Those with weakened immune systems are more likely to be infected with TB. In the 1980s, TB was on the rise in the developed world because of the emergence of HIV/AIDS, which weakens the immune system. Still today, TB is a leading cause of death among those who are HIV-positive.

Tuberculosis is diagnosed using skin and blood tests, as well as x-rays. Treating TB is a lengthy process, often taking several months and many medications. Once successfully treated, a person is likely no longer contagious. Isoniazid and rifampin are two commonly used antibiotics.

Unfortunately, some strains of TB are antibiotic resistant. Antibiotic resistance develops when the antibiotic fails to kill all the bacteria, which can happen when a course of antibiotics is not completed, and surviving bacteria multiply and pass on resistance. In addition to becoming resistant to commonly used antibiotics, the bacteria have even become resistant to some of the less widely used treatments making it even harder to treat.

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Tyson Brown, National Geographic Society
National Geographic Society
Production Managers
Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society
Program Specialists
Sarah Appleton, National Geographic Society, National Geographic Society
Margot Willis, National Geographic Society
Last Updated

October 19, 2023

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