I was also unaware that medieval plague appeared in three discrete forms, leading some modern scientists to speculate it may represent three distinct illnesses:
- Bubonic plague – characterized by “buboes” (severely inflamed lymph nodes). It had the lowest mortality rate (approximately 20%) and couldn’t be transmitted to other human beings unless the buboes were lanced. It could only be transmitted through flea bites of infected rats.
- Pneumonic plague – plague pneumonia, in which patients coughed up blood and easily transmitted it to other people. The mortality rate was nearly 100%.
- Septicemic plague – a hemorrhagic fever (like Ebola) resulting from Disseminated Intravascular Coagulation (DIC), a condition in which a patient’s blood can’t clot and they bleed from all their orifices and into subcutaneous tissues. Non-transmissible to other humans, it was 100% fatal.
The plague recurred in Europe 15 times, every decade or so. The last European outbreak ended in 1676. It would take 300 years for the continent to return to its pre-plague population of 150 million.