In the map above, one red dot is placed in each U.S. county where a case of plague has been contracted. Black plague spread to western North America from China in the late 1800's, probably entering through the port of San Francisco, and has now spread eastward as far as the Mississippi. It is now present in animals throughout the western United States, as well as in southwestern Canada.
A second black plague map, shown below, indicates the world distribution of the disease and of infected rodents as of 1997. Black plague is also known as bubonic plague, or simply "plague". Other major regions where animals carry plague are southern Africa and central Asia.