History textbooks have got it wrong about the Black Death, which they say was caused by bubonic plague spread by rats and their fleas. A new study suggests that it was in fact caused by an Ebola-like virus transmitted directly from person to person.
If the findings are confirmed it could mean that a modern form of the Black Death can emerge without requiring the insanitary conditions of the Middle Ages.
Generations of schoolchildren have been told that the plague bacteria transmitted by flea bites caused the great pestilences of medieval Europe which first appeared in the 14th century and killed at least 25 million people – more than a quarter of the entire population – over a 300-year period. But two infectious disease specialists who have analysed the Black Death have concluded that it bears a closer resemblance to modern outbreaks of haemorrhagic fever caused by the Ebola virus.
They also claim that a key mutation in a gene that protects people against infection by the Aids virus is estimated to have appeared at about the same time as the Black Death and served a similar function in that it gave carriers some protection against the virus.
Both observations point to an Ebola-like virus – rather than bubonic plague bacteria – being responsible, according to professors Christopher Duncan and Susan Scott, of the University of Liverpool.
"Intuitively, the Black Death has all the hallmarks of a viral disease rather than one caused by plague bacteria. The history books are wrong, there's little doubt about that," said Professor Duncan, who studies the way epidemics spread.
The first recorded outbreak of the Black Death occurred at the Sicilian port of Messina in 1347 and was brought in by Genoese galleys returning from the Crimea on the Black Sea.
A year later the disease arrived in the West Country of England and soon spread to towns and cities where it caused fear and panic among a superstitious population who thought the red blotches on the chest of affected individuals were "God's tokens".
Professor Duncan said people soon learnt that the only effective way of dealing with the Black Death was to put affected families and even entire villages into quarantine for 40 days. "A quarantine period was first instituted in the city states of northern Italy in the late 14th century and this was gradually adopted throughout Europe and maintained for the next 300 years until the plague disappeared," professors Duncan and Scott say in their book Biology of Plagues.
A quarantine would not have been effective if the disease was spread by rat fleas," said Professor Duncan. "Rats don't respect quarantines. This disease was transmitted directly from person to person which suggests an infectious virus."
Bubonic plagues spread in a complex fashion because they rely on the interaction of fleas, rats and people. Yet the pattern of spread of the Black Death was relatively simple and predictable, indicating person-to-person transmission.
"Endemic bubonic plague is essentially a rural disease because it is an infection of rodents," the book says. "The Black Death, in contrast, struck indiscriminately in the countryside and towns."
The symptoms of the Black Death point to a haemorrhagic fever caused by an Ebola-like virus. The fever struck suddenly, it caused aching and bleeding from internal organs, as well as red blotches caused by the effusion of blood under the skin – classic symptoms of Ebola-like illnesses.
Professor Duncan said there was further evidence to back his theory in the form of a mutation in a key gene – called CCR5 – involved in conferring some protection against HIV. Scientists have found that this mutation arose only in Europe at about the time of the Black Death and its high frequency suggests it probably offered resistance against the virus.
Professor Duncan said: "Historians jumped on the bubonic plague idea in the early 20th-century when the disease was first described in India but ... it was certainly not the causative agent in the Black Death or in any other of the outbreaks in England."Reuse content