The Black Death - the plague that could rise again

                                            Yersinia pestis                                  Shutterstock

The pandemic of COVID-19 has focussed attention on the risks to humanity of acquiring zoonotic diseases (diseases from animals). Some earlier zoontic diseases that had plagued the human race through the ages seemingly disappeared but that is not the reality. They remain potent threats living in proximity to humans and always with the possibility of breaking out again. One of these bacterium is best known by the name it acquired in the Middle Ages - 'The Black Death' or in one of its forms, the Bubonic Plague.

The Black Death is a pathogen from the bacterium, Yersinia pestis (or Y pestis), and constantly circulates in a host of rodents such as rats, mice, marmots, gerbils, ground squirrels and similar species with the fleas coming from these rodents being the vector of transmission to humans. Being abundant and spread across the planet means eradication is not possible and every continent is affected except Australia.

Essentially the plague comes in three forms: the bubonic stage where the bacterium invades lymph nodes in the armpit, neck and groin causing unsightly dark swelling; the septicaemic stage where it spreads throughout the blood stream enabling the bacterium to be recycled back into parasites; and the pneumonic stage where the lungs are invaded and the plague can be passed from human to human through respiratory droplets inhaled from the air or from surfaces.

The plague struck fear throughout Europe and the Middle East during the Middle Ages from 541 AD through the 13th to 16th Centuries leaving an indelible mark on folk law and stories from those periods. It faded from view after that time with only sporadic outbreaks in distant countries but never completely disappeared. There was an outbreak in Madagascar in 2017 killing 202 people and infecting 2,348 in total with the World Health Organisation now deeming it a re-emerging disease. More concerningly blood samples taken from people in Madagascar and wild animals have displayed levels of antibiotic resistance to all current antibiotics.  An antibiotic resistant Y pestis is a development the world could do without.