Yersinia pestis (YP) is a rod-shaped bacterium associated with the pandemic plagues that have devastated human civilization multiple times. According to available genetic evidence, an ancestral bacterium called Yersinia pseudotuberculosis (YPT) gave rise to this bug in China, from where it spread repeatedly westward to the rest of the world causing disease in both animals and humans.
In the first part, I described the Gram-negative bacillus Yersinia pestis as the etiological agent of human and animal disease; in part deux, I detailed the three major plague pandemics that have devastated human civilization many a times – the modern incarnation of which, complete with medical and epidemiological records, is known to have been caused by Yersinia pestis. In this third and final part, let me tell you about the ancient pandemics.
The first known use of the noun ‘plague’ occurred in the 14th century, according to The Merriam-Webster. The word has Latin, Old High German and Greek roots, all of which point to tragedy, lamentation, and curse. In modern English, the severity of the word has become diluted somewhat; it is now also used to depict unwelcome, nuisance events or mild disturbances. But it is important not to be unmindful of the disaster, the destruction, the calamity – untold misery and suffering of countless people, that this word came to represent during certain periods of human history.