Y. pestis mainly infects rats and other rodents. Rodents are the
prime reservoir for the bacteria. Fleas function as the prime vectors
carrying the bacteria from one species to another. The fleas bite the
rodents infected with Y. pestis and then they bite people and so
transmit the disease to them.
Transmission of the plague to people can also occur from eating
infected animals such as squirrels (e.g., in the southeastern U.S.)
Once someone has the plague, they can transmit it to another person
via aerosol droplets.
History — Yersinia is named after a Swiss bacteriologist Alexandre-
Emile-Jean Yersin (1863-1943) who identified it in 1894 after a trip
to Hong Kong looking for the agent that was killing thousands of
people in southern China. The same discovery was made at the same
time by a Japanese bacteriologist Shibasaburo Kitasako.
The plague has been responsible for devastating epidemics. The
disease occurs endemically (at a consistent but low level) in many
countries including the United States. “La Peste” (The
Plague), a novel (1947) by the Nobel Prize-winning French writer
Albert Camus (1913-1960) is set in the Algerian city of Oran overrun
by a deadly epidemic of the plague.
Bioterrorism — The General Accounting Office, the investigative arm of the US Congress, in a 1999 report considered plague to be a “possible, but not likely” biologic threat for terrorism, as it is difficult to acquire a suitable strain of Y. pestis and to weaponize and distribute it. Seed stock is difficult to acquire and to process and heat, disinfectants and sunlight render it harmless.
The plague is also known as pest and pestis.