Origin of the Thembisa model


Many mathematical models have been developed to describe different aspects of the South African HIV epidemic. Thembisa was developed in an effort to synthesize four previously-developed models, each of which has different strengths and limitations:

Thembisa incorporates many of the elements of these previously-published models. In addition it also includes a number of new features not included in any of the previous models (for example, modelling of male circumcision and pre-exposure prophylaxis).


Versions of the Thembisa model


Two versions of the Thembisa model have been developed: a model programmed in C++ and a model programmed in Excel and Visual Basic for Applications (VBA). The Excel/VBA model and its outputs can be downloaded for free (see Downloads). The Excel/VBA version has the advantage of being easy to use (especially for individuals without computer programming experience) but is slow to run. The C++ model is much faster to run and is therefore used for the purpose of uncertainty analysis and calculation of 95% confidence intervals around model outputs. However, the C++ model is not user-friendly in its current form, and is therefore not yet publicly available.


The Thembisa model has been applied to South Africa as a whole as well as each of the nine provinces. The default assumptions in the model relate to the country as a whole, but a file with province-specific assumptions can be downloaded and used to generate province-specific results.


A number of versions of the Thembisa model have been published:


Model developers


Dr Leigh Johnson is an actuary and epidemiologist, based at the Centre for Infectious Disease Epidemiology and Research, at the University of Cape Town.


Professor Rob Dorrington is an actuary and demographer, based at the Centre for Actuarial Research, at the University of Cape Town.




The following organizations have funded the development of the Thembisa model: