Endemicity (or disease intensity) is a measure of disease prevalence in a particular region and prevalence is the proportion of people infected at a given point in time. We predict the prevalence of malaria parasites at different locations to provide estimates of endemicity. We present these predictions in the form of maps.
We predict endemicity, or disease intensity, within areas of stable malaria transmission. The vast majority of malaria disease and death occurs within these areas and the level of endemicity within these areas is of particular interest to groups involved in malaria control. Information about areas of unstable malaria transmission is important for regions that are close to malaria elimination and it is more appropriate to measure disease incidence in these areas (see Spatial limits of transmission).
Areas suffering the same level of endemicity often have similar characteristics of disease spread, which can help experts assess the severity of the local malaria problem and, to some extent, what needs to be done.
There are no hard and fast rules about how to classify the intensity, or endemicity, of malaria disease. Over time some standards have evolved but different countries, people and groups prefer different approaches.
Classes of endemicity
Within areas of stable malaria transmission, we have subdivided the level of malaria endemicity into three risk classes. These classes are pertinent to control using the most widely deployed malaria control method, insecticide-treated nets (ITNs).
Endemicity is measured as the percent of people in a community who are infected with malaria parasites at a given point in time. In the lowest risk class (≤5%), control with ITNs is relatively easy. In the intermediate risk class (>5% to <40%), models predict that malaria can be controlled if everyone uses an ITN every night. In high risk areas (≥40%), additional measures, in combination with universal coverage of ITNs, are required to control malaria.