Fig. 4: LISA cluster maps of the SAA index.

LISA cluster maps show the localized spatial autocorrelation of the SAA index for communities throughout Malawi. Clusters are areas where all communities have a significantly (assessed at α = 0.05) lower SAA index (blue) or higher SAA index (red) than surrounding communities. The map also shows areas that are spatial outliers: areas where communities with a low SAA index (light blue) are surrounded by communities with a significantly higher SAA index or where communities with a high SAA index (pink) are surrounded by communities with a significantly lower SAA index. Areas that were neither part of clusters or spatial outliers are shown in light gray. Clusters in blue show the geographic location of HIV treatment deserts. Clusters in red show the geographic location of clusters of abundance. a–f, LISA cluster maps are shown for the six catchment sizes explored in the spatial sensitivity analysis, based on walking for a maximum of 1 h (a); walking for a maximum of 2 h (b); walking for a maximum of 3 h (c); using a combination of motorized transportation, bicycling and walking for a maximum of 1 h (d); using a combination of motorized transportation, bicycling and walking for a maximum of 2 h (e); and using a combination of motorized transportation, bicycling and walking for a maximum of 3 h (f).