Human Immunodeficiency Virus Increases the Risk of Tuberculosis Due to Recent Re-infection in Individuals with Latent Infection

HIV-associated TB disease can follow reactivation of latent Mycobacterium tuberculosis infection or recent (re-)infection with M. tuberculosis. If contemporary TB cases share identical M. tuberculosis strains (i.e., are “clustered”), the episode is likely to have followed recent (re-)infection, irrespective of evidence of previous latent infection. Individuals experiencing a first TB episode between 1996 and 2008 in Karonga District, Northern Malawi, were included if information on M. tuberculosis infection status (from tuberculin tests) before 1990 and a DNA fingerprint from the TB episode were available. The researchers explored differences in proportion clustered by prior M. tuberculosis infection status and HIV status, adjusting for age, sex, bacille Calmette-Guérin scar status, and time since tuberculin testing. Of 79 HIV-negative TB cases, those with previous M. tuberculosis infection were much less likely to be clustered than cases without prior infection (29% vs. 77%, adjusted OR = 0.15, 95%CI 0.04-0.59). Among 119 HIV-infected TB cases, clustering was similar in both groups (88% vs. 84%, adjusted OR = 1.85, 95%CI 0.41-8.29). HIV infection appears to increase the risk of TB following recent re-infection in patients with latent M. tuberculosis infection. Results add to the mounting evidence that HIV-associated TB mainly follows recent M. tuberculosis infection.

 The International Journal of Tuberculosis and Lung Disease. 2010 Jul; Volume 14, Number 7: 909-15.