Minimum spanning networks (MSN) visually describing discrete genetic distance between unique haplotypes of the RVFV M genome segment within the greater east African lineage. Each node represents one nucleotide difference between extant (open circle) or inferred (black filled circle) haplotypes. Proportionally larger open circles or squares represent the relative number of extant haplotypes represented in the network. Generally, squares denote the predicted progenitor haplotype for each lineage, whereas circles indicate progeny haplotypes. Note the greater distance as measured in nucleotide changes (steps) between the Kenya-1 and Kenya-2 lineages than with the prototype Kenyan 1997–1998 RVFV strain. Also note the star-like phylogeny of the Kenya-1 lineage indicating the potential for increases in virus population size or geographic range. An asterisk indicates the relative position of the putative M segment reassortant virus (strain #0608). Adapted from .