The outbreak of plague in India has prompted a rash of potted histories of the events of 1348-50, when something like 1.4 million English people, from a total population of little more than 4 million, died of disease.
In the Indian epidemic the main killer has been pneumonic plague, but bubonic plague is active too, a surprising echo of the medieval scourge.
But it may be a false echo, for at least one expert disputes the connection. He accepts that bubonic plague is present in India; but he doubts it was the same disease that killed so many in 14th-century England.
Ten years ago Graham Twigg, a zoologist at the University of London's Royal Holloway College, published The Black Death: A Biological Reappraisal. He argued that, from what we know of the many outbreaks of bubonic plague in the modern world the same disease could not have caused the Black Death.
Twigg's study caused only a ripple of interest at the time. He says: 'Scientists were more ready to consider it than historians, (who) have a fixed view and do not want to change it.'
Philip Ziegler, the author of the classic study, The Black Death, published in 1969, said last week: 'I have never heard of Twigg's book. It sounds very interesting.'
But Twigg is not the only doubter. Two years after Ziegler's book came out, the late Professor J F D Shrewsbury, an eminent bacteriologist, surveyed the evidence and concluded that, though bubonic plague was about, it could not have killed as many people as is claimed. The death toll, he thought, must have been exaggerated.
The notion that the cause of the Black Death was bubonic plague carried by rats can have arisen only this century. It was 1894 before the bacillus Pasteuris pestis was identified in Hong Kong, and it was only in the early years of this century that the role of rodents (often, but by no means exclusively rats) and the flea in human infection was proven. Much of the detective work was done by the British Plague Commission in India.
The story Ziegler tells of the origins of the Black Death drew on the medical and epidemiological research from the turn of the century, and on studies by the World Health Organisation. It is now so well known as to be almost part of our folklore. It goes like this: bubonic plague was endemic in parts of central Asia before a series of natural disasters disturbed the ecology of the region and drove the rodents, fleas and bacillus westwards from their natural habitat. Ziegler wrote: 'It was, above all, rattus rattus, the tough, nimble, by nature vagabond, black rat that made the move.' Carrying the fatal flea, it invaded the Middle East and then Europe, reaching the south coast of England in 1348, perhaps on the ships of returning Crusaders.
The rest is history. Plague recurred many times - but never as disastrously as in the Black Death - and abated only in the 17th century with a last swipe at London in 1665. A small outbreak killed a few people in Suffolk in 1910.
This was the story that Twigg used to trot out to his students, until he came to question it. 'It suddenly struck me that here we have a tropical disease with very specific requirements for its success: how could it operate in a cold north European climate?'
And he knew that the black rat, which had certainly arrived in England at or before the onset of the Black Death, was not a 'vagabond' by nature. It was confined to the artificial warmth of ships and houses and rarely ventured into the countryside. Today it is an endangered species in Britain. The larger, tougher, ground-living brown rat (rattus norvegicus) did not arrive until 1728.
What struck Twigg most forcibly was that well- documented modern outbreaks of bubonic plague, such as the epidemic which killed millions in India at the turn of the century, were nothing like as virulent as whatever caused the Black Death. Even in tropical climates where the disease should have been at its most potent, it never wiped out one-third of the population.
He thought once that the true culprit in the Black Death might be anthrax, but he is not sure now. He is convinced, however, that it was not bubonic plague.
'He is right to be sceptical,' says John Hatcher, reader in economic history at Corpus Christi College, Oxford. 'We have never seen anything like the Black Death. But I do not find his objections to the bubonic plague theory a hurdle.'
Hatcher's view remains the received wisdom. He thinks it was a freak instance of bubonic plague, in which a very rare coincidence of circumstances turned it into a bigger killer than it has ever been since. 'It may only happen once every 10,000 years. That's all one can say about it.'
This may be reassuring not only for India, but for California too. Bubonic plague has been endemic there since 1900, living in marmots in the high sierras behind Hollywood. Sometimes ground squirrels bring it close to town and vets catch it from pampered pets. But if they call it the Black Death they may be wrong.
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