Paul D. van Helden is Professor of Medical Biochemistry and Director of the MRC Centre for Molecular and Cellular Biology, based at the University of Stellenbosch Faculty of Health Sciences. He trained as a protein chemist and switched to molecular biology during and after his post-doctoral training. In the last ten years, he has focussed his research largely on tuberculosis, particularly molecular epidemiology. He serves and has served on a variety of local and national bodies, such as the Medical and Dental Council of SAand grant review panels for national and international bodies. He is a past-president of the SA Society of Biochemistry and Molecular Biology and has received the Gold medal award of that society.
The economic divide: Politics, research and control of TB in the developing world
As Western society progressed through the industrial revolution, the incidence of TB reached unprecedented levels. As these societies gained wealth, the incidence of disease declined even in the absence of sophisticated diagnostics and treatments in contrast to the developing world. The economic divide shows an inverse correlation to the incidence of TB. The WHO DOTS programme to combat TB has been promoted universally, but is one programme (a universality) likely to work in different civilizations and under different economic conditions? Thus it is necessary to consider aspects of TB research and control in the context of the different world regions and view the disease as a local (community) problem as well as a global problem. In this context the microbe that causes TB is necessary but not sufficient to cause disease. A changed environment and gross defects in social organisation are some of the factors leading to the re-emergence of tuberculosis. A country by country comparison of incidence rates for tuberculosis parallels quite closely a similar plot of social and political unrest.
The economic divide is also clearly illustrated by varying incidence rates which may be as low as 8/100 000 pa or as high as 540 (or more)/100 000 pa which is a 60-fold difference. This sixty-fold difference in incidence rates closely parallels the 60 fold differences in per capita income and health expenditure in developing and developed countries. Where the incidence of tuberculosis is increasing, we would expect the reproductive rate (R0) to be >1. Under these conditions the epidemic can rapidly advance because of compounding. Even at an increase of 3.5% per annum we can expect a doubling of the caseload after 20 years. In Zimbabwe for example, the incidence rate showed a 3-fold increase in just 6 years which approximates to a compound increase of approximately 20% per annum. Under these conditions we may rapidly reach a situation similar to that experienced in the newly industrialised world in the 18th and 19th centuries, where approximately 20-25% of all deaths were due to tuberculosis. This situation today is particularly alarming given the emergence of multidrug resistant TB. This is particularly evident in the states of the former USSR, where drug resistance is rife. Despite the gloomy statistics and predictions, there is reason for hope. Firstly, the incidence of TB in the newly industrialised world of the 18th and 19th centuries declined despite the absence of antibiotics and because of improvements in living conditions. Secondly, we have effective drugs which, if delivered correctly will effect good cure rates. Thirdly, the diagnosis and treatment of tuberculosis (drug sensitive) is not particularly expensive. Finally, a reason for optimism is that the worse the situation appears, the better the potential for improvement.