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Location of spatial-only primary clusters of P. falciparum prevalence in Gezira state in each year from 1999 to 2009. Primary spatial clusters are shown as pink circles of varying radius or red zeros (when a cluster radius is indeterminate). The location of all primary spatial-only clusters, except in 2007 and 2009, appears not vary by large distances and are concentrated in area in south of the Gezira state.
