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. 2011;6(10):e25098.
doi: 10.1371/journal.pone.0025098. Epub 2011 Oct 10.

Burden of new and recurrent tuberculosis in a major South African city stratified by age and HIV-status

Robin Wood  1 , Stephen D Lawn, Judy Caldwell, Richard Kaplan, Keren Middelkoop, Linda-Gail Bekker
Affiliations

Burden of new and recurrent tuberculosis in a major South African city stratified by age and HIV-status

Robin Wood et al. PLoS One. 2011.

Abstract

Aim: To 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.

Methods: Details 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.

Results: The 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.

Conclusions: The 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.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Population age and gender pyramid of Cape Town at mid-year 2009.
Data based on South African census data .
Figure 2
Figure 2. The numbers of tuberculosis notifications in 2009, which were recorded as HIV-infected, HIV-uninfected and of unknown HIV-status, stratified by 5-year age group.
Figure 3
Figure 3. The numbers of tuberculosis notifications of new and recurrent disease in patients with known HIV-negative status, stratified by 5-year age group.
Figure 4
Figure 4. Notification rates for all, new and recurrent tuberculosis cases for HIV-negative residents aged 15 years to 49 years in Cape Town.
HIV-uninfected population denominators derived from the product of Cape Town age population pyramid , and 1-HIV-prevalence .
Figure 5
Figure 5. The estimated cumulative risk for new (initial) and retreatment episodes of tuberculosis between birth and 75 years of age for Cape Town residents remaining HIV-uninfected.
Figure 6
Figure 6. The numbers of tuberculosis notifications of new and recurrent disease in patients with known HIV-infection, stratified by 5-year age group.
Figure 7
Figure 7. Notification rates for all, new and recurrent tuberculosis cases for HIV-positive residents aged 20 years to 54 years in Cape Town.
HIV-infected denominators derived from the product of Cape Town age population pyramid , and HIV-prevalence .
See this image and copyright information in PMC

References

    1. World Health Organization. Global tuberculosis control. World Health Organization, Geneva.; 2009. Epidemiology, strategy, financing. WHO/HTM/TB/2009.411 Accessible at the following URL: http://www.who.int/tb/publications/global_report/2009/en/index.html. Accessed 1st March 2011.
    1. World Health Organization. Global tuberculosis control. A short update to the 2009 report. WHO, Geneva, 2009.; 2009. Accessible at the following URL: http://www.who.int/tb/publications/global_report/2009/update/tbu9.pdf Accessed 1st March 2011.
    1. Cape Town TB Control - Progress Report 1997-2003 Available at URL http://www.hst.org.za/publications/618 Accessed 1st March 2011.
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