Do Incarcerated Populations Serve as a Reservoir for Tuberculosis in South Africa?

Abstract

Tuberculosis (TB) prevalence among incarcerated populations is as much as 1,000 times higher than in the general population. This study evaluates whether correctional facilities serve as a reservoir through which TB is transmitted to surrounding communities. Tuberculosis test data were extracted from the South African National Health Laboratory Service database for patients tested for TB between 2005 and 2011. We conducted graphical analysis to assess the relationship of TB rates between incarcerated and non-incarcerated populations over time. We performed generalized linear modeling with a log link function to assess TB risk in communities surrounding correctional facilities, net of confounders. We assessed linkages between incarcerated and non-incarcerated populations over time using Granger causality analysis. Tuberculosis prevalence among incarcerated populations was four times higher than in the general population. Tuberculosis incidence rates in incarcerated and non-incarcerated populations followed similar trends over time. The presence of a correctional facility in a municipality was associated with 34.9% more detected TB cases (confidence interval: 11.6-63.2; P < 0.01), controlling for potential confounders. Detected TB in incarcerated populations did not have predictive power in explaining detected TB rates in the non-incarcerated population after controlling for serial correlation in the time series data. Despite high TB prevalence, trends in correctional facilities do not appear to be driving temporal trends in the general population. However, correctional facilities still act as a TB reservoir that raises the overall TB risk in the vicinity. Intensified TB control policies for correctional facilities, formerly incarcerated individuals, and surrounding communities will reduce TB prevalence overall.

Figure 1.

Total number of detected incident cases of tuberculosis (TB) (A) and multidrug-resistant TB (MDR-TB) (B) in the incarcerated population and the general population over time. Notes: quarterly totals calculated from original sample of 13,188,651 TB tests. Incarcerated populations were identified by testing location. Source: National Health Laboratory Service database. This figure appears in color at www.ajtmh.org.

Figure 2.

Case-positive test rates for tuberculosis (TB) (A) and multidrug-resistant TB (MDR-TB) (B) in the incarcerated population and the general population over time. Notes: case-positive rate is the number of incident TB or MDR-TB cases per 100 TB tests performed. Incarcerated populations were identified by testing location. Source: National Health Laboratory Service database. This figure appears in color at www.ajtmh.org.

Figure 3.

Total number of tuberculosis (TB) tests performed in incarcerated and general population over time. Notes: quarterly counts of TB tests. Incarcerated populations identified by testing location. Source: National Health Laboratory Service database. This figure appears in color at www.ajtmh.org.

Figure 4.

Total number of detected incident cases of tuberculosis (TB) (A) and multidrug-resistant TB (MDR-TB) (B) in municipalities with correctional facilities, municipalities without correctional facilities, and the incarcerated population over time. Notes: quarterly counts of TB cases. Cases defined as positive test result more than 2 years since last positive test. Multidrug-resistant TB cases identified from test results for specimen resistant to both rifampicin and isoniazid. Incarcerated populations were identified by testing location. Source: National Health Laboratory Service database. This figure appears in color at www.ajtmh.org.