Malaria: old infections, changing epidemiology

The epidemiology of malaria has always varied between different parts of the world because of widely varying vectorial capacity. Mortality from malaria can be measured from clinical records or the rise of mortality during an epidemic, but better from observing the fall of mortality during control or from the population frequency of protective host genes. Holoendemic malaria may have doubled the infant and young-child mortality rate in Africa in the recent past, but death rates have fallen because of chemotherapy. The epidemiological pattern is changing. In the Sahel, water-resource developments tend to lengthen the transmission season, though less than might be expected, and urbanization tends to decrease transmission in Africa, not in Asia. The spread of multiple drug resistance of the parasites is making case management harder and deaths may rise. Malaria control has always been unsatisfactory in sub-Saharan Africa owing to the highly effective vector. The main current hopes for control are the use of the effective insecticideimpregnated bed nets and better case management. No simple concept of an epidemiological transition can reflect the very diverse changes occurring in human malaria worldwide.