h I n this age of molecular biology, the healthcare industry, politicians and the community at large are trying to find 'magic bullet' drugs and vaccines to conquer disease. Although smallpox has been eradicated and polio may soon be a scourge of the past, many pathogens replicate rapidly and mutate prodi-giously, enabling them to evolve ways to circumvent our immune systems, as well as our drugs and vaccines. To fight and win the war against new emerging infections such as HIV/AIDS, TB and now SARS (severe acute respiratory syn-drome), it is important to understand the temporal and spatial dynamics of the pathogens in human and, in some cases, animal reservoirs or vector populations. It is also necessary to understand the complex web of socio-economic factors pertinent to controlling the spread of disease, so that feasible, affordable and, most importantly, effective public-health policies can be devised and implemented. Beyond magic bullets Host–pathogen interactions, embed-ded in their ecological or socio-economic settings, are complex, non-linear systems that cannot be understood without the help of detailed mathematical and statisti-cal analyses. The most important ingredi-ent in such analyses, however, is the skill required to build dynamical systems and statistical models then used to derive the necessary insights. Unlike physical systems that have canonical theories to guide and direct the construction of models, biological systems are too com-plex to yield to codified laws of Nature. Modelling biological systems is an art as much as it is a science, requiring experi-ence with and dedication to the biological problems at hand, as well as a sound technical knowledge of appropriate mathematical and statistical theories. While South Africa has many talented scientists trained in quantitative methods, relatively few of them have been drawn into the modelling and statistical fields of epidemiology. A decisive infrastructural investment is needed to address the health crises in Africa. Prior to the advent of HIV, for instance, tuberculosis was kill-ing half-a-million people in Africa each year but now, because of the virus, it is responsible for a tenfold increase in mortality rate in some African countries. Furthermore, there is a growing threat from drug-resistant strains of malaria, another major cause of morbidity and mortality. The initiative we describe below is designed to enhance capacity across Africa to collect data and conduct quantitative analyses necessary to under-stand the dynamics of the major diseases afflicting the continent. The success of this initiative will be mea-sured in terms of the number of profes-sionals trained to apply mathematical modelling to the disease challenges that we face. It will also be assessed by the extent to which such professionals are recruited to staff disease-control centres across Africa with a mandate to collect and analyse the data necessary to help formulate effective public-health policies at a regional level. This means persuading some of the very best students to pursue careers as quantitative epidemiologists and professionals in health care policy rather than becoming physicists, engi-neers, economists, and policy-makers in academia and industry.