Last updated at 16:21 BST, Thursday, 13 October 2011

Secrets of the plague

Summary

14 October 2011

The genetic code of the germ that caused the Black Death has been reconstructed by scientists for the first time.

The Black Death, also known as the plague, killed millions of people in Europe in the 14th Century.

Reporter:
Matt McGrath

Skeletons of plague victims

DNA samples were taken from skeletons found in London

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Humans have rarely encountered an enemy as devastating as the bacterium, Yersinia pestis. Between 1347 and 1351 it sparked the Black Death, an infection carried by fleas that spread rapidly across Europe killing around 50 million people.

Now scientists have uncovered some of the genetic secrets of the plague, thanks to DNA fragments drilled from the teeth of victims buried in a graveyard in East London.

The researchers say that all current strains circulating in the world are directly related to the medieval bacterium. And while the infection still kills 2,000 people globally every year, it's much less of a threat because our immune systems have adapted to it.

The scientists say the techniques used to rebuild the genome of the Black Death could now be used to reconstruct other ancient pathogens

Matt McGrath, BBC World Service

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Vocabulary

rarely encountered

not often met or come into contact with

devastating

destructive and harmful

sparked

caused to start

fleas

tiny jumping insects which feed on the blood of animals and humans

fragments

small, incomplete pieces of

victims

people who had died of the disease

strains

versions of the disease

immune systems

our body's natural defence mechanism

adapted

changed and evolved to be able effectively to fight

pathogens

small organisms that cause diseases