Causes

  • Tuberculosis (TB) is caused by the infectious bacterium Mycobacterium tuberculosis.1 When air contaminated with M. tuberculosis is inhaled, the bacteria can enter the lungs, resulting in TB infection.

– TB can be transmitted when a person with active TB coughs or sneezes, expelling M. tuberculosis into the air

  • A person with latent TB may lead a healthy life without progressing to active TB disease2

– of the 2 billion people currently estimated to have latent TB infection, fewer than 10 million a year develop active TB2

  • For people living with HIV (PLWHIV) who have been exposed to M. tuberculosis, the risk of developing TB is estimated to be between 20–37 times greater than in people without HIV infection3,4
  • People living with HIV (PLWHIV) in congregate settings such as prisons and refugee centres have a higher risk and incidence of TB than people residing outside of these settings4

– crowded living conditions facilitate transmission of TB, including multi-drug-resistant TB4

  • Mycobacterium africanum is a sub-species of the M. tuberculosis complex found in West Africa, where it causes up to half of human TB cases5

– unlike M. tuberculosis, M. africanum can also infect animals
– infection with M. africanum responds to regular TB treatment5

 

References

  1. National Institute of Allergy and Infectious Diseases: Tuberculosis - Cause. Accessed 26 November 2011.
  2. World Health Organization. Tuberculosis IGRA TB Tests Policy Statement 2011. Accessed 26 November 2011.
  3. World Health Organization. Guidelines for Intensified Tuberculosis Case-finding and Isoniazid Preventive Therapy for People Living with HIV in Resource-constrained Settings. Accessed 25 November 2011.
  4. Getahun H, Gunneberg C, Granich R, Nunn P. HIV Infection-Associated Tuberculosis: The Epidemiology and the Response. Clin Infec Dis 2010;50:S201–S207.
  5. de Jong BC, Antonio M, Gagneux S. Mycobacterium africanum—review of an important cause of human tuberculosis in West Africa. PLoS Negl Trop Dis. 2010;4(9):e744.