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BLACK DEATH UPDATE October 14, 2011

Posted by wmmbb in Humankind/Planet Earth, Social Environment.

Without immunity the population of Western Europe was vulnerable to the bacteria that has now being subjected to DNA analysis of plaque germs taken from corpses in a London Cemetery. Several conditions favoured the spread of the Black Death in the 14th Century.

ABC News provided more information:

“The Black Death was the first plague pandemic in human history,” said Johannes Krause, lead researcher and a professor at the University of Tuebingen in Germany.

“Humans were [immunologically] naive and not adapted to this disease,” he said in an email exchange.

No bug or virus has wiped out a greater proportion of humankind in a single epidemic than the Black Death.

Brought to Europe from China, it scythed through the continent from 1347 to 1351, killing about 30 million people – about one in three of Europe’s and nearly one in 12 of the world’s population at the time.

Remarkably, more recent variants of the bacterium hardly vary compared to the original microbe, says the paper.

“Based on the reconstructed genome, we can say that the medieval plague is close to the root of all modern human pathogenic plague strains,” Professor Krause said.

“The ancient plague strain does not carry a single position that cannot be found in the same state in modern strains.”

This deep similarity between ancient and modern plague calls into question the long-held assumption that virulence-enhancing mutations are what made Y. pestis so deadly to the Middle Ages.

Like Native American Indians who were exposed to smallpox, Europeans had never been exposed to the bacterium, Professor Krause said.

“Plague was among the strongest sources of selection on the human population in the last few thousand years,” he added.

“People who were less susceptible due to mutations might have survived, and these [beneficial] mutations may have spread.”

Another likely factor that worsened the Black Death’s toll was social conditions, which were far worse compared to the 18th or 19th centuries.

Poverty and malnutrition were rampant, and even the concept of hygiene was non-existent.

The onset of the so-called “Little Ice Age” could also have favoured the spread of the disease which, like many pathogens, travels more quickly in cold climes.

The same goes for the rats that carried the blood-sucking insects – fleas or lice, perhaps both – that transmit the disease.

Indeed, the species of rodent, Rattus rattus, that sowed terror across a continent in the 14th century is not the same as the one that transports plague today, Rattus norvegicus, Professor Krause said.

The 1918-19 Spanish flu pandemic killed, by some estimates, 50 million people. In absolute terms, this was the deadliest pandemic in human history.

But with a world population that was close to 2 billion, the toll in relative terms was far smaller than that of the Black Death, when the number of humans was in the hundreds of millions.

The first outbreak of plague occurred in China more than 2,600 years ago before reaching Europe via Central Asia’s “Silk Road” trade route, according to a molecular “family tree” – mapped out last year – of 17 Y. pestis strains.

It then spread to Africa, probably by an expedition led by Chinese seafarer Zhang He in the 15th century.

In the late 19th century, plague came to the United States from China, arriving in the ports of California via Hawaii, according to this evidence.

This research appears to contradict the suggestion that rats were not the primary carriers of the bacteria. The earlier post sources in part from The Guardian provides graphic accounts of the effects on people.



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