Credit: PEDRO SA DA BANDEIRA, FOR MALARIA CONSORTIUM

Where malaria is rife, millions of people die of the disease each year, significant parts of the workforce are incapacitated and tourism suffers. The impact of malaria could be exacerbated by climate change, because the Plasmodium parasites that cause the disease thrive in the warmth. Their reproduction rate has been estimated to rise by a factor of up to three by 2050 based on climate projections.

But according to Peter Gething and colleagues (Nature 465, 342–345; 2010), any climate-induced increases in the prevalence of malaria should be easy to overcome with moderate efforts at disease control. The researchers studied global maps of malaria occurrence in about 1900, and the prevalence of the Plasmodium falciparum parasite in 2007, to see how the burden of malaria has changed. The maps show that the geographical extent of malaria has dropped dramatically during this period, despite undisputed climate warming. The disease covered about 58% of the Earth's land surface in 1900, but only about 30% at the start of the twenty-first century. In addition, in three quarters of the locations where malaria was common in 1900, the number of secondary infections generated from a single infection with the parasite plummeted by more than one order of magnitude between the two surveys. Any expansions of the disease due to twentieth-century temperature rise were thus vastly overcompensated by other factors.

The success in the fight against malaria is likely to be mostly attributable to the sustained implementation of measures to control the disease, as well as to urbanization and economic development. Disease control measures are most effective at the fringes of the regions where malaria prevails — the same locations where climate change is assumed to play the largest role by expanding the current geographical extent of the disease.

In light of the historical evidence, the international community needs to face one important conclusion: if we fail to contain this crippling disease in the course of the next century, we cannot offload the blame on climate change.