Malaria is a killer. According to Jeffrey Sachs and Pia Malaney (see below) "there are 300 to 500 million clinical cases every year, and between one and three million deaths, mostly of children, are attributable to this disease. Every 40 seconds a child dies of malaria, resulting in a daily loss of more than 2,000 young lives worldwide."
Malaria also slows economic growth in developing countries. Gallup and Sachs look at The Economic Burden of Malaria (The American Journal of Tropical Medicine & Hygiene, January/February 2001). Sachs and Malaney examine: The Economic and Social Burden of Malaria (Nature, February 2002). Jeffrey Sachs has a web page on his work on malaria at the Earth Institute: Prof. Jeffrey D. Sachs on Malaria . The page provides access to published and unpublished papers, datasets, and general background.
According to Sachs and Malaney, bottom-up estimates of the costs of malaria cases, obtained by summing estimates of the costs of medical care and lost income for individual cases, are generally much smaller than the top-down estimates from looking at patterns in aggregate national data. They argue that the gap is created by behavioral responses to life in a malarious environment that are counter-productive for growth. These behavioral responses create costs beyond the care costs and income losses for individual cases. While the empirical evidence on how these behavioral responses work themselves out sounds relatively limited, they speculate that the following processes may be relevant: