What is tuberculosis?

Tuberculosis, or TB, is still one of the major causes of preventable death in the world. TB is an infectious disease caused by TB bacteria (Mycobacterium tuberculosis): a smart but deadly survivor with the cunning ability to evade our immune system. The bacterium first of all has a sort of harness: an almost impenetrable, unique surface which protects the bacterium from attacks by our immune system and antibiotics. In addition, the bacterium comes armed with a wide arsenal of proteins, secreted in order to manipulate and cunningly avoid our immune system. Macrophages (literally ‘big eaters’) are part of our immune system. They are specialized in consuming harmful microorganisms.
However, the TB bacterium manages to stay alive and multiply inside the macrophages. In the end, the macrophage is so full of bacteria that the cell dies. Other macrophages rush in to get rid of the dead cell and, in turn, are infected with TB bacteria and so on and so forth. A healthy person will not immediately become ill. In fact, one quarter of the world’s population is walking around with a ‘sleeping’ form of the TB bacterium. Things go wrong for people with a weakened immune system, because this will allow the TB bacterium to gain the upper hand and kill its host.

Signs and symptoms

The signs and symptoms of active TB (disease) are coughing, sometimes with sputum or blood, chest pains, weakness, weight loss, fever and night sweats. TB most often affects the lungs. It can cause serious damage to the lungs and other organs.

TB is curable and preventable. The vast majority of people with TB can be cured, if rapidly and accurately diagnosed; and if appropriate medicines are provided and are taken properly. But without proper tuberculosis treatment up to two thirds of people ill with TB may die.

TB infection is spread from person to person through the air when people with lung TB cough, sneeze or spit. When a person develops the disease TB, the symptoms may be mild for many months. This can lead to delays in seeking care, and results in transmission of the bacteria to others. An individual with undiagnosed and untreated lung TB disease may infect ten to fifteen other people through close contact.

Latent TB infection

An estimated quarter of the world’s population has latent TB infection, which means a person has been infected by TB bacteria but is not (yet) ill with the disease and cannot transmit the disease.
People infected with TB bacteria have a lifetime risk of 10 percent of falling ill with TB. The body’s immune system is often strong enough to prevent the development of the disease. However persons with compromised immune systems, such as people living with HIV, malnutrition, or diabetes, or people who use tobacco, have a much higher risk of falling ill.



KNCV has been fighting TB since its establishment in 1903. Over the past 120 years, the organization has acquired indispensable knowledge and experience in the field of effective TB prevention and care, resulting in pre-elimination in the Netherlands and significant contributions to global evidence generation, policy development and TB program implementation worldwide.

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