Causes

Causes

• Tuberculosis (TB) is caused by the infectious bacterium Mycobacterium tuberculosis. ¹ When air contaminated with M. tuberculosis is inhaled, bacteria can enter the lungs, resulting in tuberculous infection.
  
  • TB is transmitted when a person with active TB coughs or sneezes, expelling M. tuberculosis in the air.
• A person with latent TB can lead a healthy life without progression to active TB disease ²
  • Of the 2 billion people currently estimated to have latent tuberculosis infection, less than 10 million a year develop active TB ²
• For people living with HIV (PLHIV) who have been exposed to M. tuberculosis, the risk of developing tuberculosis is estimated to be 20 to 37 times higher than in people without HIV ^{3, 4}
• People living with HIV (PLHIV) in collective institutions such as prisons and refugee centers have a higher risk and incidence of TB than people who live outside these settings ⁴
  • Overcrowded conditions facilitate the transmission of TB, including multi-drug resistant TB ⁴
• Mycobacterium africanum is a subspecies of the M. tuberculosis complex found in West Africa, where it causes up to half of the cases of human tuberculosis ⁵
  • Unlike M. tuberculosis, M. africanum can also infect animals
  • Infection with M. africanum responds to the treatment of normal TB ⁵

References

1. National Institute of Allergy and Infectious Diseases: Tuberculosis – Causes   consulted on November 26, 2011.
2. World Health Organization. Tuberculosis IGRA TB Test Policy Statement 2011 . Retrieved on November 26, 2011.
3. World Health Organization. Guidelines for intensification of TB case detection and preventive therapy with isoniazid for people living with HIV in resource-limited settings . Retrieved on November 25, 2011.
4. Getahun H, Gunneberg C, Granich R, Nunn P. HIV infection associated with tuberculosis: epidemiology and response . ClinInfectDis 2010; 50: S201-S207. 
5. de Jong BC, Antonio M, Gagneux S. Mycobacteriumafricanum-review of an important cause of human tuberculosis in West Africa . PLoSdesdTropDis. 2010; 4 (9): e744.