|Description:||This image depicts a black rat, Rattus rattus, which is one of the amplification hosts associated with the spread of “Black Death”, or plague. Rats infected with the plague bacteria, Yersinia pestis, host fleas, which ingest the rat’s infected blood, in turn themselves becoming infected. If these fleas then bite a human being in order to obtain another blood meal, they transfer these bacteria, thereby, infecting the human with plague.|
Plague is transmitted from animal to animal and from animal to human by the bites of infective fleas. Less frequently, the organism enters through a break in the skin by direct contact with tissue or body fluids of a plague-infected animal, for instance, in the process of skinning a rabbit or other animal. Plague is also transmitted by inhaling infected droplets expelled by coughing, by a person or animal, especially domestic cats, with pneumonic plague. Transmission of plague from person to person is uncommon and has not been observed in the United States since 1924 but does occur as an important factor in plague epidemics in some developing countries.