Figure 2. . A) Predicted geographic distribution in central and western Africa of suitable environments for monkeypox virus transmission on the basis of the Maxent algorithm (www.cs.princeton.edu/~schapire/maxent/). Gray shading represents suitable environmental conditions identified by the algorithm; circles indicate localities of human monkeypox cases used to build the ecological niche models. Stars indicate localities reported during the human monkeypox outbreak in southern Sudan in 2005. B) Scatterplot using the first 3 principal components (PC1, PC2, and PC3) of the environmental variables in sub-Saharan Africa. Gray dots, environmental conditions in the entire area; black dots, suitable conditions identified by the ecological niche models; human monkeypox case localities; green squares, localities where monkeypox was reported in southern Sudan. Inset shows scatterplot scale.