Changes in Tuberculosis Disease Burden Among South African Adolescents, 2005-2015

Background: South African adolescents have a high force of Mycobacterium tuberculosis (MTB) infection, exceeding 10% per annum, which acts as a barometer of tuberculosis (TB) transmission. We described temporal changes in adolescent TB notification rates to evaluate impact of TB and HIV control measures and inform public health strategy. Method: We conducted a cross-sectional analysis of patient-level TB case data obtained from a regional health authority in Western Cape Province, South Africa, for the decade 2005–2015. Numerators were annual TB notifications (HIV-related and HIV-unrelated); denominators were mid-year population estimates from the national census, adjusted for population growth. Period averages of TB rates were obtained using Auto-Regressive Integrated Moving Average (ARIMA) time series modeling. The Agresti Coull method was used to derive confidence intervals for TB rates. Temporal trends in TB rates were explored using the Mann-Kendall test. Findings: The average adolescent TB notification rate was 477 (95% Confidence Interval (CI): 313–641) per 100,000 for all cases (all-TB) and 361 (CI: 280–441) per 100,000 for microbiologically confirmed cases. However, the adolescent all-TB rate fell by 45% from 662 to 361 per 100,000 (p=0·005) and the microbiologically-confirmed TB rate by 38% from 492 to 305 per 100,000 (p=0·008) between 2005-2015, driven mainly by rapid decreases for the period 2005–2009 (p=0·028 and p=0·027, respectively). Between 2005–2009, 21% (156/732) of adolescent TB notifications were HIV tested, 12% (19/156) of whom were HIV-positive. In the general population, the proportion of HIV-positive persons receiving antiretroviral therapy (ART) increased from <1% in 2005 to 55% in 2015. Interpretation: The encouraging fall in adolescent TB rates between 2005–2009 is not explained by timing of ART roll-out. The subsequent plateau in adolescent TB, coupled with increased rates in younger children, suggests that additional interventions are needed to sustain advances in TB control. Funding Statement: This analysis received no specific funding. Declaration of Interests: All other authors have no other potential conflicts of interest to declare. Ethics Approval Statement: Ethical approval was obtained from the University of Cape Town Human Research Ethics Committee (HREC REF 163/2016).