General Information: This strain was isolated prior to 1985 and belongs to the antiqua biovar. It can ferment rhamnonse and melibiose which is a property usually associated with Yersinia pseudotuberculosis. Strain Angola belongs to a group of atypical Yersinia pestis strains with genotypic similarities that are intermediate between Y. pestis and Y. pseudotuberuclosis strains. Genotypic studies indicate that strain Angola is the oldest Y. pestis strain analyzed to date. It carries three plasmids that are similar to other Y. pestis plasmids but have aberrant sizes. The critical virulence factor, the V antigen, is different than that encoded by typical strains of Y. pestis and there is a deletion that affects the F1 operon. Strain Angola has been shown to be virulent by aerosol in mice.