In the past, malaria had a global distribution that is now largely restricted to the tropics. Our spatial limits maps have been developed to show the borders between areas where we predict there is a malaria risk and those that are malaria free. These maps also show the districts or provinces where the malaria risk is very low. This is particularly relevant to groups working on the elimination of malaria.
Our definition of “regions where the malaria risk is very low” is less than 1 clinical case of malaria per 10,000 people in the population per year (often written as API<0.1‰). This is an important threshold used in malaria control decision-making and these regions are referred to as areas of unstable malaria transmission.
We predict which category of risk (or malaria transmission) an area falls into using data on malaria cases collected by Ministries of Health in each country and combining this with data on temperature and aridity. Each of the two important malaria parasites is treated separately. The more deadly parasite species, Plasmodium falciparum, has a smaller range because it is less able to be transmitted in colder and drier conditions compared to the second major parasite species, Plasmodium vivax. The maps are further refined by excluding areas such as a city or island that have been verified as malaria free. Each map is accompanied by full details of how it was constructed.