Article

How Soon after Infection with HIV Does the Risk of Tuberculosis Start to Increase? A Retrospective Cohort Study in South African Gold Miners

Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK.
The Journal of Infectious Diseases (Impact Factor: 6). 02/2005; 191(2):150-8. DOI: 10.1086/426827
Source: PubMed

ABSTRACT

Infection with human immunodeficiency virus (HIV) increases the risk of tuberculosis (TB), but no study has assessed how this risk changes with time since HIV seroconversion.
The incidence of pulmonary TB was estimated in miners with and those without HIV infection in a retrospective cohort study. HIV test results were linked to routinely collected TB, demographic, and occupational data. The rate ratio (RR) for the association between HIV status and TB was estimated by time since HIV seroconversion, calendar period, and age.
Of the 23,874 miners in the cohort, 17,766 were HIV negative on entry, 3371 were HIV positive on entry, and 2737 seroconverted during follow-up (1962 had a seroconversion interval of < or =2 years). A total of 740 cases of TB were analyzed. The incidence of TB increased with time since seroconversion, calendar period, and age. TB incidence was 2.90 cases/100 person-years at risk (pyar) in HIV-positive miners and was 0.80 cases/100 pyar in HIV-negative miners (adjusted RR, 2.9 [95% confidence interval {CI}, 2.5-3.4]). TB incidence doubled within the first year of HIV infection (adjusted RR, 2.1 [95% CI, 1.4-3.1]), with a further slight increase in HIV-positive miners for longer periods, up to 7 years.
The increase in the risk of TB so soon after infection with HIV was unexpected. Current predictive models of TB incidence underestimate the effect of HIV infection in areas where TB is endemic.

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Available from: Pam Sonnenberg
    • "In the recent times, AIDS epidemic has had an immense bearing on the clinical presentation, transmission and epidemiology of TB worldwide (Pawlowski et al., 2012). TB is predominantly caused by the pathogenic mycobacteria M. tuberculosis; however, non-tuberculous or attenuated strains of mycobacteria such as Mycobacterium avium, Mycobacterium kansasii, Mycobacterium fortuitum, Mycobacterium xenopi and Mycobacterium bovis Bacillus Calmette– Guérin (BCG) cause opportunistic infections in HIV patients (Juffermans et al., 1998; Smith et al., 2001; Bachmeyer et al., 2002; Karakousis et al., 2004; Serra et al., 2007; Singh et al., 2007; Azzopardi et al., 2009; Hesseling et al., 2009) even before T-cell depletion is apparent (Sonnenberg et al., 2005). More than 90 species of Mycobacterium had been reported to inhabit natural (air, water, soil or other organisms) and artificial (chlorinated municipal water) reservoirs (Primm et al., 2004). "
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    • "The main feature of immunosuppression in AIDS patients is the manifest loss of CD4 þ T cells, in the blood, lymphoid tissues, and mucosa, which is obviously an important contributor to the increased risk of developing active TB (Moir et al. 2011). However, susceptibility to TB increases soon after HIV infection, far before the decrease of the CD4 þ T-cell counts below 500 cells/mL (Sonnenberg et al. 2005), clearly showing that the mechanisms underlying the increased susceptibility of HIV-infected individuals to active TB goes beyond the CD4 þ T-cell drop. In fact, the World Health Organization (WHO) recommends the initiation of antiretroviral therapy for any HIV-infected individual who develops TB, regardless of the CD4 þ T-cell counts (WHO 2013). "
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