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).


CONCLUSIONS
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.
Houben
R M G J
RM
Infectious Disease Epidemiology Unit, London School of Hygiene & Tropical Medicine, London, UK. Rein.Houben@lshtm.ac.uk
Glynn
J R
JR
Mallard
K
K
Sichali
L
L
Malema
S
S
Fine
P E M
PE
French
N
N
Crampin
A C
AC
D016000:Cluster Analysis; D016172:DNA Fingerprinting; D015658:HIV Infections / Q000150:complications*; D006801:Humans; D008295:Malawi / Q000453:epidemiology; D017720:Molecular Epidemiology; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D012008:Recurrence; D012307:Risk Factors; D014376:Tuberculosis / Q000209:etiology* / Q000382:microbiology