What is Tuberculosis? Tuberculosis (TB) is a contagious bacterial infection caused by Mycobacterium tuberculosis, Mycobacterium, bovis, or Mycobacterium, africanum. Tuberculosis refers to disease most commonly caused by M. tuberculosis. Although other mycobacteria can cause diseases that mimic TB, those infections are not contagious, and most respond poorly to drugs that are very effective against TB.

How Can a Person Contract TB?

A person can contract TB after inhaling air contaminated with M. tuberculosis . For the air to become contaminated, a person with active TB must cough or sneeze and release bacteria which may remain in the air for several hours. However, a fetus may acquire TB from its mother before or during birth. In developed countries children may become infected by another mycobacterium, M. bovis, which can be transmitted through unpasteurized milk. The usual site of the disease is the lungs, but other organs may be involved. The first infection is known as the primary infection. TB develops in a minority of people whose immune systems do not successfully destroy the primary infection. The disease may occur within weeks after the primary infection or it may lie dormant for years before causing clinical symptoms. In pulmonary (lung) TB, the disease can vary from minimal to massive involvement of the lungs, but without effective therapy the disease becomes progressive. TB that affects other parts of the body (extrapulmonary TB) usually comes from pulmonary (lung) TB that spreads through the blood.

Risk Factors: At Risk Persons to Contract TB

The risk of contracting TB increases with the frequency of contact with people who have the disease, poor social conditions, inadequate nutrition and overcrowding. The elderly, young children and individuals who are immunocompromised (for example, those with acquired immunodeficiency syndrome (AIDS), those undergoing immunosuppressivetherapy, or transplant recipients taking anti-rejection medications) are at a higher risk for rapid progression of the disease.


An increase in the incidence of TB has been seen recently. Over 1.5 million TB cases per year occur in Sub Saharan Africa. Factors that have contribute to the increase in TB incidences include;

  • an increase in HIV infection rate, and
  • the appearance of drug resistant strains of mycobacterium; incomplete treatment of TB infections is a contributing factor to the proliferation of drug resistant strains of the bacteria.


Primary TB is symptomless in a great majority of individuals. TB in the lungs, which is the commonest site of growth, may cause an infected person to simply feel unwell or have a cough that is blamed on smoking or a recent episode of flu. The classical symptoms include cough, mild (low-grade) evening fever, profuse night sweats, weight loss, and fatigue. There are many other symptoms depending on the organ affected.


The following examinations are useful in the diagnosis of tuberculosis. Chest X-Ray: an abnormal chest Xray is usually the first indication of TB in diagnostic evaluation of a vaguely ill patient. Sputum staining: sputum is stained with Ziehl-Nielsen (ZN) stain for acid and alcohol fast bacilli(AAFB) Sputum cultures: sputum is cultures on Dover's or Lowenstien-jensen medium for 4-8 weeks. Tuberculin skin test: this is performed by injecting a small amount of protein derived from TB between the layers of skin, mainly in the forearm. Two days later the injection site is checked for swelling and redness. Bronchoscopy: this is useful in cases where sputum is not available. Biopsies of the pleura, lymph nodes and solid lesions within the lungs may be required to make the diagnosis PREVENTION BCG(Bacille Calmette-Guerin) vaccination-the value of this vaccination is controversial and is used only in those countries where the likelihood of contracting TB is very high. Contact tracing-screening of individuals who have close contact with a infected person. Use of anti TB drug isoniazid is very effective when given to people at a high risk of contracting the disease.


Anti-tubercular drugs can usually cure even the most advanced cases of tuberculosis. Successful treatment lies in continual self administration of drugs for 6 months (usually daily doses of rifampicin, isoniazid, pyrazinamide and others). Longer drug regimes may be necessary for atypical tuberculosis infections. Hospitalization is indicated in order to prevent spread of the disease to others until the infectious period is over, usually 2 to 4 weeks after the start of therapy.

CDC - Tuberculosis (TB)
Tuberculosis, or TB By WHO
Prevention & Control of Tuberculosis
Tuberculosis - MayoClinic
Bronchiectasis and Tuberculosis

Last Updated on Tuesday 18th January 2011