(This information is not intended to be a substitute for the advice of a doctor or a recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the advice of a doctor for your specific condition.)


TB, or Koch’ Pulmonum (KP), is a bacterial infection that causes more deaths in the world than any other infectious disease.
•    When TB becomes active, it kills 60% of those who are not treated. This amounts to 3 million deaths worldwide every year.
•    When treated, 90% of patients who have an active TB infection survive.

TB is an infection caused by a bacterium called Mycobacterium tuberculosis. TB spreads from person to person through air as a person with active TB coughs, sneezes, or expels air. After a person becomes infected, the TB bacteria are controlled by the person’s immune system. The infection becomes latent, or confined. When the bacteria spread out of control, the infection becomes active. Since most infected people breathe out only a few bacilli when they exhale, transmission of TB usually only occurs after one or more months of exposure to someone with active TB. Each person with active TB disease will infect on average between 10 and 15 people every year.

Special white blood cells called macrophages attack TB bacteria. Many of the bacteria die. TB bacteria have a cell wall made of a complex waxy material. This wall protects some bacteria inside the macrophage! Special cells of the immune system surround and separate the infected macrophages. The mass resulting from the separated, infected macrophages are hard, grayish nodules called tubercles.
• About 90% of infected people heal completely after the initial infection. The tubercles calcify and the bacteria cannot break out again.
• For about 10% of infected people, the TB bacilli may remain confined within the tubercles for years. This is called latent TB. Latent means dormant or sleeping. The bacilli inside the tubercles become active sometime later in life when their immune system becomes weak. The bacilli could break out of the tubercles in the alveoli and spread to the lungs and other sites of the body through the bloodstream and lymphatic system. This is called active TB.

The early symptoms of active TB include: weight loss, fever, night sweats and loss of appetite. Some patients may have little or no symptoms with TB. As more lung tissue is destroyed and granulomas expand, cavities develop in the lungs, and sometimes expand into larger lung airways. This allows large numbers of bacilli to spread when the patient coughs.  Granulomas can also eat away at blood vessels, causing bleeding in the lungs, which could result in bloody sputum.

Latent TB or initial infection can be diagnosed with a skin test called a Mantoux test (tunerculin test). This test can identify most people infected with tubercle bacilli 6-8 weeks after initial exposure. A substance called PPD is injected under the skin in the forearm and examined 48-72 hours later. If a red welt forms around the injection site, the person may be infected with M. TB, but the disease is not necessarily active. A blood test known as IGRA (Interferon Gamma Release Assay) can also show if a patient has been exposed or is infected with M. TB.

To diagnose active TB, a doctor relies on symptoms, the patient’s history of exposure to TB, and x-rays that may show evidence of TB infection, usually in the form of cavities or lesions in the lungs. The doctor will also take sputum and other samples to be examined by a pathologist.

People with latent TB infection have TB germs in their bodies, but they are not sick because the germs are not active. These people do not have symptoms of TB disease, and they cannot spread the germs to others. They have a normal chest x-ray and a negative sputum test. However, they may develop TB disease in the future. They are often prescribed treatment to prevent them from developing TB disease. Because there are less bacteria in a person with latent TB infection, treatment is much easier. Usually, only one drug is needed to treat latent TB infection. The medicine usually taken for the treatment of latent TB infection is called isoniazid (INH). INH for 9 months is the preferred regimen. INH kills the TB bacteria that are in the body.

A person with active TB disease has a large amount of TB bacteria in the body. TB disease can be treated by taking several anti-TB drugs for 6 to 12 months. People who have been treated for at least two weeks are usually not contagious anymore. Patients who do not take their medications as often and as long as prescribed, give the bacteria a chance to become resistant to the treatment.

TB can be prevented through good hygiene, including good ventilation and covering the mouth when coughing.

(Source:  WHO & U.S. Centers for Disease Control and Prevention)