The prevalence of malaria in more than a third of the 108 countries affected by the disease halved between 2000 and 2008, thanks largely to increased aid aimed at prevention, said the World Health Organization.

Margaret Chan, WHO director general, said in a foreword to the World Malaria Report 2009, “that the tremendous increase in funding for malaria control is resulting in the rapid scale up of today’s control tools.” In particular she singled out the increased use of insecticide treated mosquito nets.

However, the report found that cases fell least in countries with the highest incidence rates—for example, Uganda, Burkina Faso, Kenya, Congo, Malawi, Pakistan, and Nigeria.

These countries …