Understanding the Three Variants of the Medieval Plague: Bubonic, Pneumonic, and Septicemic

Throughout history, the Black Death and the Great Plague of 1665 have been the subject of much confusion and misinformation. These two pandemics, though separated by several centuries, were crucial in shaping public health measures and medical understanding. However, it is essential to clarify that these were distinct events involving variations of the Yersinia pestis bacterium, which manifested in three primary forms: Bubonic, Pneumonic, and Septicemic. Let's delve into the specifics of each variant to better understand the Black Death and the Great Plague of 1665.

Bubonic Plague

The Bubonic Plague was the most common form of the disease during these historical outbreaks. This variant targeted the lymph nodes, causing them to swell and eventually burst. The swelling of the lymph nodes, scientifically known as lymphadenopathy, is the hallmark symptom of bubonic plague. Without treatment, the fatality rate of the Bubonic Plague could reach up to 50%. Despite its prominence during the Black Death and the Great Plague of 1665, the bacteria responsible can still be found today, particularly in the United States, where it poses a risk, especially in areas with high black rat populations.

Pneumonic Plague

The Pneumonic Plague is a particularly severe and dangerous form, primarily affecting the lungs. This variant caused typical pneumonia-like symptoms such as shortness of breath, chest pain, and a cough with watery or bloody mucus. Unlike Bubonic Plague, Pneumonic Plague has the unique characteristic of being human-transmissible. In the absence of contemporary treatment, the fatality rate was almost 100%, making it a deadly and transmissible threat.

Septicemic Plague

The Septicemic Plague was the least understood in historical times, as it attacked the bloodstream causing massive tissue death and turning the skin black, hence the term "Black Death." The causative agent, the Yersinia pestis bacterium, enters the bloodstream, leading to septicemia. This form of the plague had a mortality rate of up to 90% and was extremely difficult to treat effectively. It was transmitted by fleas rather than human-to-human contact, but close and direct contact could also lead to transmission.

Historical Context and Differing Variants

While popular belief often conflates the historical events of the Black Death and the Great Plague of 1665, it is important to note that these were distinct occurrences, each with its unique combination of the aforementioned variants. The term "black plague" typically refers to the Great Plague of 1665 in England, which involved significant transmission of the disease. The Great Plague saw three distinct variants: Bubonic, Pneumonic, and Septicemic. The overall mortality rates were significantly higher for the more severe forms like Septicemic and Pneumonic, with estimates ranging from 80-90%.

Regarding the terminology, it is noteworthy that the term "Black Death" wasn't commonly used until the mid-1700s. The name "Black Death" was a misnomer given the actual visual manifestations of the disease, which involved blackened tissue and skin due to extensive tissue death and the disease’s rapid spread through the bloodstream and lungs. Additional variants such as the de Novo strain of plague, while not as prominent during these historical outbreaks, can still cause serious health issues today, especially in regions with high rat populations.