Archaeologists and forensic scientists studying 14th century skeletons exhumed from a London neighborhood have concluded that the bubonic plague which ravaged Europe and much of the known world during that century may have started out as an infection spread by rat fleas, but soon mutated into a much more virulent and deadly human-to-human airborne disease.
The Observer reports the scientists examined the teeth of the 25 skeletons, which were discovered by railroad workers building London’s Crossrail project on the edge of Charterhouse Square in Farringdon last March. The researchers believe that the bubonic plague, also called the Black Death, mutated from a bacteria spread by the bites of infected fleas living on black rats to a more virulent airborne strain passed between people.
This pneumonic plague variety infected victims’ lungs, causing it to be spread by coughing, the scientists believe. The more virulent strain also killed victims much faster– normally within a day– and spread more rapidly in the crowded, unsanitary European cities of the day.
The result was the deadliest pandemic in human history, with around 75 million people succumbing to the plague during the course of the 14th century. Some researchers believe that as much as half the known world’s population died during the outbreak.
“As an explanation for the Black Death in its own right, [bubonic plague is] simply not good enough,” Dr. Tim Brooks, an infectious diseases expert at Public Health England, said of the new findings. “It cannot spread fast enough from one household to the next to cause the huge number of cases that we saw during the Black Death epidemics.”
“In a small number of people … the organism will spread to their lungs and they will then develop a pneumonia. It is that critical switch, that if there were enough people in contact with them, that allows it to spread as a pneumonic plague,” Brooks explained.
Terrifying news of a horrific and incurable disease ravaging the East first reached London in 1347. The following summer, bubonic plague struck London, killing some 40,000 residents, or about half the city’s population. At the height of the Black Death, so many Londoners were dying each day that the dead were unceremoniously buried five deep in mass graves.
Between 1348 and 1665, a new wave of the plague struck London approximately once every 20-30 years, with around a fifth of the city’s population dying during each new outbreak.
There are still periodic and sporadic outbreaks of the bubonic plague to this day. Last year, dozens of people in Madagascar died from the disease.