Abstract
AimTo describe the burden of tuberculosis (TB) in Cape Town by calculating TB incidence rates stratified by age and HIV-status, assessing the contribution of retreatment disease and estimating the cumulative lifetime TB risk in HIV-negative individuals.MethodsDetails of TB cases were abstracted from the 2009 electronic TB register. Population denominators were estimated from census data and actuarial estimates of HIV prevalence, allowing calculation of age-specific and HIV-stratified TB notification rates.ResultsThe 2009 mid-year population was 3,443,010 (3,241,508 HIV-negative and 201,502 HIV-positive individuals). There were 29,478 newly notified TB cases of which 56% were laboratory confirmed. HIV status was recorded for 87% of cases and of those with known HIV-status 49% were HIV-negative and 51% were positive. Discrete peaks in the incidence of non-HIV-associated TB occurred at three ages: 511/100,000 at 0–4 years of age, 553/100,000 at 20–24 years and 628/100,000 at 45–49 years with 1.5%, 19% and 45% being due to retreatment TB, respectively. Only 15.5% of recurrent cases had a history of TB treatment failure or default. The cumulative lifetime risks in the HIV-negative population of all new TB episodes and new smear-positive TB episodes were 24% and 12%, respectively; the lifetime risk of retreatment disease was 9%. The HIV-positive notification rate was 6,567/100,000 (HIV-associated TB rate ratio = 17). Although retreatment cases comprised 30% of the HIV-associated TB burden, 88% of these patients had no history of prior treatment failure or default.ConclusionsThe annual burden of TB in this city is huge. TB in the HIV-negative population contributed almost half of the overall disease burden and cumulative lifetime risks were similar to those reported in the pre-chemotherapy era. Retreatment TB contributed significantly to both HIV-associated and non-HIV-associated TB but infrequently followed prior inadequate treatment. This likely reflects ongoing TB transmission to both HIV-negative and positive individuals.
Highlights
Tuberculosis (TB) notifications in South Africa have increased progressively over the last 20 years, temporally associated with the growth of the HIV epidemic
TB in the HIV-negative population contributed almost half of the overall disease burden and cumulative lifetime risks were similar to those reported in the pre-chemotherapy era
African TB cases in 2007 was estimated to be 74%, but this figure was extrapolated from a minority of notified cases who were tested in that year, potentially leading to over-estimation of HIV prevalence
Summary
Tuberculosis (TB) notifications in South Africa have increased progressively over the last 20 years, temporally associated with the growth of the HIV epidemic. Testing for HIV-infection among TB cases has remained low due to stigma, doctor reluctance and operational constraints. African TB cases in 2007 was estimated to be 74%, but this figure was extrapolated from a minority of notified cases who were tested in that year, potentially leading to over-estimation of HIV prevalence [1,2]. In South Africa in 2007 HIV-testing was performed on 39%. In 2009, HIV-status was determined for 87% of all TB notifications, enabling stratification of the majority of TB cases by HIV-infection status
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