Shigellosis, which caused by Shigella and enteroinvasive Escherichia coli (EIEC), was still a threat to public health. Compelling evidence indicates that Shigella species and EIEC are derived from multiple origins of E. coli and form a single pathovar. EIEC strains are regarded as precursors of 'full-blown'Shigella evolved from E. coli. By gain and loss of functions, Shigella and EIEC became successful human pathogens through convergent evolution from diverse genomic backgrounds.