There was also a decline in papal authority and

strengthened. There was also a decline in papal authority, and people lost faith in a Catholic
Church that was powerless to stem the tide of death” 3 .
In the late 1800s researchers discovered that the plague is caused by a rod-shaped
bacterium called Yersinia pestis that is transmitted by fleas. These fleas predominantly affect
small animals such as rodents; humans are accidental hosts. When a flea bites a host, it ingests
the bacteria. The bacteria then multiply in blood clot in the foregut of the flea which blocks the
flea’s bloodsucking apparatus. The flea is then unable to take blood into its foregut so it
“becomes hungrier, and in this ravenous state, bites the host repeatedly; with each bite, it
regurgitates plague bacteria into the wound” 4 . With each bite, it spreads the plague bacteria and
the infection starts. Fleas with heir foregut completely blocked will eventually starve to death. If
the flea lives and its host dies, the flea responds by moving off the body and seeking another
3
Irwin W. Sherman. “Bubonic Plague” in Encyclopedia of Insects 2009 , ed. Vincent H. Resh and
Ring T. Carde (Oxford: Elsevier Science & Technology)
4
Irwin W. Sherman. “Bubonic Plague” in Encyclopedia of Insects 2009 , ed. Vincent H.
Resh and Ring T. Carde (Oxford: Elsevier Science & Technology)
Irwin W.
Sherman. “Bubonic Plague” in Encyclopedia of Insects 2009, ed. Vincent H. Resh and
Ring T. Carde (Oxford: Elsevier Science & Technology)

3
warm-blooded host. If there is an extensive die off of preferred hosts such as rodents, the flea
may move on to a less preferred host such as a human. This is how the epidemic begins
When a flea bites a human, the bacteria are released into the body and travel to the lymph
nodes. The lymph nodes swell and become sore. These swollen lymph nodes are known as
buboes and can appear on the neck, armpits, and/ or groin. A few days after the buboes appear,
the victim may experience high fever, delirium, and hemorrhages in the skin resulting in black
splotches. “Some contend that these dark spots on the skin gave the disease the name Black
Death, whereas others believe “black” is simply a mistranslation of “pestis atra” meaning not
black, but a dark or sinister disease”
5
. The buboes continue to enlarge and can sometimes reach
the size of an egg; when they burst, it is extremely painful. When the plague settles in the lungs it
is called pneumonic plague. It can happen when someone inhales the bacteria from someone
with the disease. The disease can also spread to the lungs if someone with the plague is not
treated. It is characterized by violent coughing. The septicemic plague is another form of the