The results of tMRCA estimation are summarized in Figure 3C and 3D. In addition, sequence isolation dates were plotted against their genetic distance (units of substitutions/site) to their MRCA, to graphically show the accumulation of mutations through time ( Figure 3A and 3B). The tMRCA of all reassortant viruses (All- were isolated from central and east Jakarta (Table 1) . Parsimony reconstruction (see Methods) of binary ancestral geographical states (either Greater Jakarta or West Java) upon the HA and NA ML phylogenies suggested that the MRCA of all reassortants (and the MRCAs of each reassortant subgroup) likely originated from Greater Jakarta and surroundings (Table S2 ; result robust to random resolution of polytomies; see Methods).