Tuberculosis (TB)

Definition

Tuberculosis (TB) is an infective disease caused by the bacterium Mycobacterium tuberculosis. The lungs are the main site of infection but TB can spread to other parts of the body as well. The incidence of tuberculosis has increased after the emergence of HIV and AIDS. HIV infection weakens the person’s immune system and therefore makes a person vulnerable to secondary infections such as tuberculosis. Inadequately treated tuberculosis infections may lead to development of drug resistant strains of tuberculosis bacteria which are difficult to treat.

Types

Tuberculosis can exist in two forms:

  • Latent TB: At times the bacteria exists in the body in a dormant state. The immune system resists the development of symptoms. The person can even remain asymptomatic for years. During this stage the tuberculosis is not contagious.
  • Active TB: Symptoms are produced during this state usually within a few weeks of exposure. The state of tuberculosis is a contagious state.

Symptoms

The smptoms of active TB include :

  • Cough lasting for more than 3 weeks.
  • Blood in the sputum.
  • Chest pain.
  • Fatigue.
  • Weakness.
  • Fever.
  • Night sweats.
  • Chills.
  • Loss of appetite.
  • Unexplained weight loss.
  • Breathing difficulties.

Tuberculosis that has spread to other parts of the body such as the bone, kidneys, liver, heart, spine or brain produces symptoms depending on the affected part of the body. For example, involvement of the vertebral bones can cause backache or involvement of kidneys causes blood in the urine.

Causes

TB is an infective disease which usually spreads through tiny respiratory droplets of the infected person when expelled by coughing, sneezing or even talking. A person can be a carrier of TB bacteria in its latent state which can later become active. People with HIV or those with weaker immunity are at a higher risk of getting TB. Even just a visit to a country or region where the disease is prevalent can put a person at risk of contracting TB.

Living in crowded conditions and malnutrition increases the risk of TB. Therefore the disease used to be considered as an infection of the poor but TB can affect any person with weakened immunity. Various diseases other than HIV infection, like uncontrolled diabetes mellitus, and the use of immune-suppressing drugs can drop the immune defenses and TB is one of the diseases that can then develop.

Treatment

Untreated tuberculosis can be fatal. Chest x-ray, MRI and CT scans, PPD tuberculin skin test and blood and sputum tests helps diagnose the condition. A prolonged course of treatment, up to 9 months of treatment with medication, might sometimes be necessary to completely eradicate the TB infection. The most commonly drugs used in TB include :

  • Rifampin.
  • Isoniazid.
  • Pyrazinamide.
  • Ethambutol.

These drugs are used in combinations for active infections to prevent drug-resistant strains from developing. A single drug can suffice for a latent infection. A program called DOT (directly observed therapy) is sometimes recommended to avoid non-compliance of medications by the patient. In this program a health worker is involved who administers the medication to the patient so that there is no chance of forgetting a dose. BCG vaccination is administered in certain countries to prevent TB infections in children.

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