Abstract

Objective: Our study uses sex-specific and age-specific HIV prevalence data from an
ongoing population-based demographic and HIV survey to infer HIV incidence and
survival in rural KwaZulu-Natal between 2003 and 2011, a period when antiretroviral
treatment (ART) was rolled out on a large scale.
Design: Catalytic mathematical model for estimating HIV incidence and differential
survival in HIV-infected persons on multiple rounds of HIV seroprevalence.
Methods: We evaluate trends of HIV incidence and survival by estimating parameters
separately for women and men aged 15–49 years during three calendar periods (2003–
2005, 2006–2008, 2009–2011) reflecting increasing ART coverage. We compare
model-based estimates of HIV incidence with observed cohort-based estimates from
the longitudinal HIV surveillance.
Results: Median survival after HIV infection increased significantly between 2003–
2005 and 2009–2011 from 10.0 [95% confidence interval (CI) 8.8–11.2] to 14.2 (95%
CI 12.6–15.8) years in women (P < 0.001) and from 10.0 (95% CI 9.2–10.8) to 14.0
(95% CI 10.6–17.4) years in men (P ¼ 0.02). Our model suggests no statistically
significant reduction of HIV incidence in the age-group 15–49 years in 2009–2011
compared with 2003–2005. Age-specific and sex-specific model-based HIV incidence
estimates were in good agreement with observed cohort-based estimates from the
ongoing HIV surveillance.
Conclusion: Our catalytic modelling approach using cross-sectional age-specific HIV
prevalence data could be useful to monitor trends of HIV incidence and survival in other
African settings with a high ART coverage.