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Tuberculosis

Biology (Year 12) - Specific Disease Studies

Ben Whitten

What is tuberculosis? Tuberculosis (TB) is caused by a type of bacterium called Mycobacterium tuberculosis. Tuberculosis is an obligate aerobe bacteria requiring oxygen in its metabolism processes. Humans are the only reservoir for Mycobacterium tuberculosis, and it is found most commonly in the lungs.

How is TB transmitted? Tuberculosis is indirectly transmitted through the air (airborne disease), not by surface contact. When a person inhales a droplet nuclei containing M. tuberculosis, the droplet nuclei traverse the mouth or nasal passages, upper respiratory tract, and bronchi to reach the alveoli of the lungs.

What is the typical pathology (signs, symptoms, and progress) of TB? There are two types of tuberculosis, being latent (bacteria are inactive in the body) and active. The signs and symptoms of active tuberculosis include:

  • Coughing for three or more weeks

  • Coughing up blood or mucous

  • Chest pain, or pain with breathing or coughing

  • Unintentional weight loss

  • Fatigue

  • Fever

  • Night sweats

  • Chills

  • Loss of appetite


Tuberculosis also has the ability to affect other parts of the body, including the kidneys, spine or the brain. When it occurs outside your lungs, signs and symptoms vary according to the organs involved.

What is the life cycle of TB? A tuberculosis infection occurs in four stages.

  • The initial macrophage response

  • The growth stage

  • The immune control stage

  • The lung cavitation stage

These four stages happen over roughly one month.

What is the pathogenicity of TB? When inhaled, tuberculosis bacteria enter the lungs, they can multiply and cause a local lung infection (pneumonia). The local lymph nodes associated with the lungs may also become involved with the infection and usually become enlarged. The hilar lymph nodes (the lymph nodes adjacent to the heart in the central part of the chest) are often involved. Where is TB present geographically? TB is most common in Africa, the West Pacific, and Eastern Europe. These regions are plagued with factors that contribute to the spread of TB, including the presence of limited resources, HIV infection, and multidrug-resistant (MDR) TB.

What are the treatments/prevention/control measures for TB? For latent TB, your doctor can prescribe tablets to reduce the risk of you developing active TB. For active TB, you will be prescribed a combination of special antibiotics, which you must take for at least 6 months. You may need initial treatment in hospital. If you complete the full treatment, you can be cured of TB disease. The vaccine for tuberculosis ­is called the Bacillus Calmette–Guérin (BCG) vaccine. The BCG vaccine does not prevent a person from becoming infected with TB if exposed to it, but it helps prevent severe or life-threatening TB disease, especially in young children. The three key strategies to advance the goals of the National TB control program are:

  • Active and passive case finding that allows the early and accurate diagnosis of persons with TB through effective clinical and laboratory services.

  • Prompt and effective free treatment of persons with active TB in supervised programs.

  • Timely surveillance and reporting of disease incidence, drug resistance and treatment outcomes nationally to inform program evaluation.

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