Tuberculosis TB

What is Tuberculosis?

Tuberculosis (TB) is a fairly common and often deadly infectious disease caused by the Mycobacterium tuberculosis bacterium. TB usually attacks the lungs (as in pulmonary TB) but can also affect the central nervous system, as well as the lymphatic, circulatory, genitourinary and gastrointestinal systems, and bones, joints, and even skin.

The emergence of strains of TB, that are resistant to the most commonly used drugs to treat the disease, is a global concern.  Although tuberculosis resistant strains are much less common than regular TB, the emergence of some strains that are resistant to all available drugs is a worry for public health and TB control experts.

How do you get Tuberculosis?

When persons infected with active TB cough, sneeze, speak, sing or spit, the tuberculosis germs are propelled into the air where they remain suspended. Uninfected people can then inhale the bacteria into their lungs. People with prolonged, frequent, or close contact with persons who are infected are at particularly high risk of becoming infected themselves. TB is highly contagious under conditions that favour transmission. The number of bacteria needed to create a new infection is very low, and inhaling just a single bacterium can cause a new infection.

Not every person who becomes infected with TB will become sick or develop symptoms. The initial infection is usually contained by the body's defense mechanisms, and the bacteria can remain dormant in the lungs for a long time, even for life without any adverse effects for the infected person. In fact, only about 5-10 percent of people who are infected with TB actually become sick or infectious, and this occurs usually later in life.

The presence of the HIV virus in a person who is also infected with TB bacteria will greatly increase the chance of developing the tuberculosis disease. TB is a leading cause of death among people who are HIV positive.

Susceptibility and Resistance

The risk of infection with TB is directly related to the length of exposure to environments where there are infected individuals. The risk of developing TB is highest in children under 3 years old, lowest in later childhood, and high again among adolescents, young adults, the very old and the immuno-suppressed.

Incubation Period

The incubation period for Tuberculosis is 14-60 days.

What are the Symptoms?

The initial infection with TB bacteria may be unapparent or consist mainly of a slight cough similar to the common cold. About 75 percent of active TB disease is pulmonary TB, with the infection occurring primarily in the lungs. When active TB begins, the symptoms of pulmonary TB include a chronic productive cough lasting for more than three weeks, coughing up blood, fever, night sweats, fatigue, chills, and weight loss. The other 25 percent of the cases are known as extrapulmonary TB, where the infection spreads to other parts of the body, such as the pleural cavity (the cavity surrounding the lungs), the meninges (the lining of the brain), the lymph nodes in the neck, the urinary system and reproductive organs, and in bones and joints . Extrapulmonary TB occurs more frequently in immuno-suppressed individuals (such as those with HIV) and in young children. Extrapulmonary TB is not contagious, however, it frequently occurs in conjunction with pulmonary TB which is highly contagious.

Preventative Measures

Travellers should avoid exposure to known TB patients in crowded environments, such as hospitals, prisons, homeless shelters, or refugee camps.  Travellers may also be exposed in family settings where a  member of the family, usually elderly, may create airborne TB germs in poorly ventilated environments.

There is a vaccine called BCG that is used in most developing countries to reduce the severe consequences of TB in infants and children. However, it is unclear if this vaccine is effective in preventing the adult forms of TB.


Tuberculosis treatment is difficult and requires relatively long courses (months) of multiple antibiotics. Successful cures for uncomplicated pulmonary TB are achieved through a six month course of four antibiotics for four months and two antibiotics for two months. Failure to cure TB and the subsequent development of resistant strains occurs when patients do not complete the recommended treatment regimen.  

Extrapulmonary TB requires more intensive therapy. Treating anyone with multiple-drug-resistant strains of tuberculosis is more difficult, requiring up to 4 to 6 drugs for 18 to 24 months.  Treatment of resistant strains should be managed by an expert in this field.



Where Does It Commonly Occur?

The bacteria that cause tuberculosis are present throughout the world.