The two main malaria prevention measures, i.e. long-lasting insecticide treated nets (LLINs) and indoor residual sprays (IRS) have contributed significantly to malaria reduction across Africa, but the progress is now leveling off, as these interventions are reaching their fundamental protective limits. In many settings, low-level residual transmission persists even where LLINs and IRS coverage already exceeds 80%. This problem is compounded by the widespread lack of accurate data on the extents and drivers of this residual transmission. This presentation will describe past and ongoing efforts to quantify and characterize existing residual Plasmodiumtransmission in communities where LLINs are already widely used, but where transmission still persists.