Human immunodeficiency virus increases the risk of tuberculosis due to recent re-infection in individuals with latent infection.

BACKGROUND

Human immunodeficiency virus associated tuberculosis (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.

METHODS

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. We 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.

RESULTS

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-positive TB cases, clustering was similar in both groups (88% vs. 84%, adjusted OR = 1.85, 95%CI 0.41-8.29).

DISCUSSION: HIV infection appears to increase the risk of TB following recent re-infection in patients with latent M. tuberculosis infection. Our results add to the mounting evidence that HIV-associated TB mainly follows recent M. tuberculosis infection.