It seems to be homologous to the I-F system found in "Yersinia pestis". Plague vaccine is a vaccine used against "Yersinia pestis". Individual cases of foxes infected with "Yersinia pestis" are known. Pneumonia caused by "Yersinia pestis" is usually called pneumonic plague. The live attenuated vaccine containing strain "Yersinia pestis" EV is used for plague immunization. It is also produced by "Yersinia pestis". Instances of presence of "Yersinia pestis", the cause of the black plague, have been reported. It is also used to visualize the classic "safety pin" shape in "Yersinia pestis". At Afanasevo Gora, two strains of "Yersinia pestis" have been extracted from human teeth. Bubonic plague is one of three types of plague caused by bacterium "Yersinia pestis". It is caused by "Yersinia pestis", a gram-negative species of bacterium. It is caused by "Yersinia pestis" and is transmitted from animal to animal by fleas. Plague is an infectious disease caused by the bacterium "Yersinia pestis". Another bacterium of the same genus, "Yersinia pestis", is the cause of Plague. Pneumonic plague is a severe lung infection caused by the bacterium "Yersinia pestis".