The origin of malaria: mixed messages from genetic diversity.

Over the past 35 years, the incidence of malaria has increased 2-3-fold. At present, it affects 300-500 million people and causes about 1 million deaths, primarily in Africa. The continuing upsurge has come from a coincidence of drug-resistant parasites, insecticide-resistant mosquitoes, global climate change and continuing poverty and political instability. An analogous rapid increase in malaria might have taken place about 10,000 years ago. Patterns of genetic variation in mitochondrial DNA support this model, but variation in nuclear genes gives an ambiguous message. Resolving these discrepancies has implications for the evolution of drug resistance and vaccine evasion.