There were three forms of the disease spread by the bacterium Yersinia pestis. The most common of these, and the one responsible for so much death and loss during the 14th century, was the bubonic plague.
This takes its name from the primary symptom: the patient will develop painful and swollen lymph nodes, which are called buboes. The bacteria that enter the body from the infected flea bite, and typically the closest lymph nodes will become the point from which the bacteria begin to multiply. These nodes often developed in a patient’s groin, neck, or armpits. If a physician or barber surgeon attempted to open these buboes, they would ooze pus and bleed heavily.
"In men and women alike it first betrayed itself by the emergence of certain tumours in the groin or armpits, some of which grew as large as a common apple, others as an egg…" G. Boccaccio, Decameron.
After this, someone suffering from the plague could be expected to endure an acute fever, reaching temperatures as high as 41°C (around 106 °F). This would be accompanied by diarrhoea and vomiting (victims can even begin to vomit blood). In some instances, the patient would also develop bizarre spots and rashes, usually black in colour, which discoloured the body. This usually affected the extremities, such as the fingers and toes. Without the correct treatment, around 80% of patients that contract bubonic plague will be dead within 8 days.
As well as being spread by the bites of infected fleas, Yersinia pestis could also be spread by person-to-person contact. When an infected person coughed, sneezed, or spread infected air droplets by some other way, then they could infect those nearby with either pneumonic or septicaemic plague. Some of the symptoms were the same for these forms of the disease, but they were more virulent and much more frightening. To contract either was, in almost every circumstance, a death sentence.
