Risk Factors

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The most commonly ascribed risk factors include:

  • Prolonged, close contact with a sputum positive patient:
    • Family members of sputum positive patient
    • Co-workers of sputum positive patient
  • Over crowded congested living conditions (environment) such as in:
    • Prisons
    • Mental asylums
    • Slums
  • Endemic (“High risk”) areas for TB (India)
  • HIV infection / AIDS
  • Diabetes
  • Renal failure
  • Immunosuppressive drugs (steroids, anticancer drugs)
  • Intra-venous drug abusers
  • Silicosis
  • Travellers
  • Children
  • Alcoholism
  • Physical / Emotional stress
  • Medical / Para-medical workers
  • Upon entering the human body, the TB germs commonly get lodged in the upper portions of any of the two lungs. The body defense mechanism tries to contain the infection. If the infection is controlled at this stage, the disease (active TB) does not manifest. If they are unable to do so, local tissue destruction of the lung occurs and the germs make their way to the lymph nodes (local police stations) which may get enlarged. However, if the above said risk factors are present, the infection spreads and the disease becomes manifest. If proper and adequate treatment is not taken, the disease can progress and involve other organs also.
  • Not all people infected with the germs of TB develop the disease. This is because of the strong body defense (immune) system, which tends to fight and overcome the infection.
  • Only 5 -10% of the people infected with germs develop the disease (active TB), though the exact cause is still not known.
  • Overall lifetime risk of developing the disease (active TB) in an infected person is 10%.
  • Close, prolonged indoor contact poses the greatest risk. The intimacy and duration of contact with an infectious patient, the degree of infectiousness of the case and environment of contact are important determinants of transmission.
  • Tuberculosis cannot be spread by touching, shaking hands, using the same utensils or sharing the same toilet with someone having tuberculosis.
  • The risk is maximum from a sputum positive patient, less from a sputum negative patient and even lower (negligible) from an extra-pulmonary TB patient.
  • Adequate sunlight (UV light) and ventilation can prove lethal to the TB bacilli and decrease the risk of infection.
  • HIV infected individuals are at a greatly increased risk of TB especially in high prevalence areas like India (overall lifetime risk of developing active TB in an infected HIV positive individual is 30 – 60 %).