Tuberculosis

Tuberculosis is an infection caused by bacteria. It's spread through the air—when an infected person coughs, sneezes, laughs, etc. However, it is not easy to become infected with tuberculosis. Usually a person has to be close to someone with TBdisease for a long period of time.

What is TB?

TB is a bacterial disease which in humans is usually caused by an organism called Mycobacterium tuberculosis (M. tuberculosis). TB is an abbreviation of the word Tuberculosis and is how people usually refer to the disease. Bovine TB is a disease caused by similar bacteria called Mycobacterium bovis (M. bovis). Bovine TB mainly affects cattle but can also affect humans. Most of the information on this website refers to TB in humans caused by M. tuberculosis. Just a few years ago it was believed that TB was an old disease, and that it was no longer a problem in humans. But now because of such issues as drug resistance and HIV, it has become a major problem again.

Latent TB

The bacteria that usually cause TB in humans, usually affect the lungs, but can affect other parts of the body. If you are infected with the bacteria you won’t necessarily become sick, because you can have either latent TB or TB disease. Latent TB occurs when a person has the bacteria within their body, but the bacteria are present in very small numbers. They are kept under control by the body’s immune system and do not cause any symptoms. People with latent TB do not feel sick and do not have any symptoms. It is usually only known that someone has latent TB because they have had a test, such as the TB skin test. People with latent TB are not infectious and cannot pass the bacteria on to other people.

TB disease

TB disease is what happens when a person has latent TB and then becomes sick. Sometimes this is known as having active TB or TB disease. Most people with latent TB never become sick. Overall about 5 to 10% of people with latent TB, who do not receive treatment for it, will become sick at some time in their lives. Some people become sick soon after they have become infected, before their immune system (the part of the body that fights diseases) can fight the bacteria. Other people don’t get sick at first but they get sick years later when their immune system becomes weak for another reason. This can be because they have an infection, such as infection with HIV, or some other health problem. Some people are known to have a higher risk of becoming ill.

What are the symptoms?

The symptoms depend on which area of the body has been infected. If someone has pulmonary disease, which is TB in the lungs, then they may have a bad cough that lasts longer than two weeks. They may also have pain in their chest and they may cough up blood or phlegm from deep inside their lungs. Other symptoms of TB include weakness or fatigue, weight loss, lack of appetite, chills, fever and night sweats.