Fig. 4

The frequency distribution of SNPs distances in hot and cold spot areas. In general, SNP distance peak of > 1000 are form differences between isolates belonging to different lineages, in this case between L2 and L4. 500–1000 are resulted from major sub-lineages such as between L2.1 and L2.2. The ones < 500 are usually from differences between more detailed sub-lineages such Asian African2 and Asian African 3. < 100 is almost definitely from the difference between isolates belonging to the same detailed sub-lineages or the same cluster