We need to know how bad the malaria situation is before we can make it better, says Robert Snow.
Despite the fanfare surrounding pledges to halve the number of malaria deaths over the next decade, the truth is that scientists have little idea how many people get sick or die from malaria, or where, let alone whether control efforts are working. Researchers lack data to evaluate accurately the impact of interventions such as drugs or insecticide-impregnated bednets. The international community must address this deficiency if it is to improve control strategies and measure their progress.
In Africa, the number of children dying of malaria has increased dramatically over the past 20 years, whereas other causes of childhood mortality have steeply declined1. Some 90% of the world's malaria deaths probably occur in Africa. But many of our assertions about baseline data for Africa and elsewhere are couched in terms of ‘probably’ and ‘likely’, because the simple truth is we do not know.
The Roll Back Malaria (RBM) initiative aspires to halve malaria deaths by 2010 (ref. 2), and the United Nations' Millennium Development Goal is to halt and then reverse the rising incidence of malaria by 2015 (ref. 3). These targets are certainly optimistic, but are they even measurable?
National data on malaria illness and death are full of gaps and inaccuracies due to under-reporting and misdiagnosis. At the Kenya Medical Research Institute in Nairobi, we are instead using satellite data and climate models linked to demographic data to provide new scientific tools for predicting on a continent-wide scale where people live in relation to mosquitoes and malaria parasites4,5.
Combining data from epidemiological studies of malaria deaths and illness, this new science is helping RBM to overcome deficiencies of national health information systems in Africa, providing more reliable estimates of the continent's Plasmodium falciparum burden6 (see map). But for other regions of the world, similar approaches have yet to be developed, or to be extended to other malaria parasites such as P. vivax.
RBM's decisions cannot be made effectively without accurate scientific data. What is needed is a properly funded, science-based strategy to evaluate the use of both existing and future control tools.
There are two relatively simple, effective and affordable interventions for malaria control: insecticide-treated bednets and artemisinin-based combination drugs.
RBM relies on national household sample surveys to monitor progress towards its goal of providing antimalarial drugs to 60% of febrile children by 2010. Current surveys report that 54% of febrile children in Africa receive an antimalarial drug7, but fail to capture information on the effectiveness, dose, timing or support of treatment. This is not surprising given that the relevant questions are buried in a national-health survey questionnaire the size of the Oxford English Dictionary.
Similarly, RBM's target of providing bednets to 60% of children is not framed scientifically to ensure that these reach the most vulnerable. The distribution often correlates more closely with wealth than areas of high malaria risk7.
In 2001, the UK government granted one non-governmental organization US$22 million to market nets in Kenya. But it focused on urban rather than rural areas. The outcome: a mere 1.5% increase in children protected — hardly a stunning success.
The best way to measure the impact of interventions would be to use rigorous, longitudinal demographic and epidemiological studies, such as those provided by the INDEPTH network of sentinel sites (http://www.INDEPTH-network.org). But such sites are few — there are only 11 in Africa. We urgently need a properly funded, science-based strategy to evaluate the use of both existing and future malaria control tools.
Clinical trials of new vaccines and drugs for malaria, such as those planned by the recently launched European and Developing Countries Clinical Trials Partnership, will eventually require sites where operational effectiveness can be measured.
More money won't be enough. Donors, governments and international initiatives must take on board the concerns of scientists in the field, and back political goals with hard science. Without a greater appreciation of the importance of creditable baseline data, and the need for adequate funding and resources to gather such data, in a decade or so we will not be celebrating the rolling back of malaria —we will be scratching our heads wondering whether we made any difference at all.