It wiped out nearly a quarter of London’s population and was one of the triggers for the scientific renaissance that swept England in the 17th Century. Now the bacteria that caused the Great Plague of London between 1665 and 1666 has been definitively identified as the bug that causes bubonic plague – Yersinia pestis.
Archaeologists used DNA testing on skeletons found in a mass grave in a churchyard uncovered during the construction of the new Crossrail Elizabeth that will run through the city’s Liverpool Street Station.
Around 42 bodies were discovered in the pit, where they had been stacked up to eight deep and once would have been in coffins and wrapped in shrouds.
It is thought the pit may have contained up to 100 individuals although some of the pit had been disturbed by building work during the 19th and 20th Century.
Scientists took samples from the teeth 20 of the skeletons to search for traces of the plague pathogen.
They found five appear to have been exposed to it before they died and the researchers believe this is most likely to be the cause of death.
Scientists now hope to sequence the whole genome of the plague bacteria in the hope of comparing it to those responsible for the Black Death epidemic in 1348.
The research could help provide new insights into the evolution of the disease as it spread around Europe over several centuries.
Professor Vanessa Harding, an expert in London history at Birkbeck, University of London, said: ‘This is a very exciting finding, for the history of London, the history of disease, and the history of burial.
‘It confirms that Yersinia pestis was present in early modern London plague epidemics, and links them epidemiologically with the 14th-Century Black Death and the 1720 Marseille plague.
‘We still need, however, to understand why the disease manifested itself in so many different ways, and whether other pathogens made a significant contribution to these epidemics.’
While Yersinia pestis has long been suspected as the cause of the Great Plague in the 17th Century, the new findings are the first to confirm it definitively.
It was the last major bubonic plague epidemic to have hit Britain and killed around 100,000 people in London.
The total death toll is likely to have been far higher, however, as many town and cities around England were hit far worse than London.
An account by Thomas Vincent in God’s Terrible Voice in the City by Plague and Fire, describes London in August 1665.
He said: ‘Now the cloud is very black, and the storm comes down upon us very sharp.
‘Now Death rides triumphantly upon his pale Horse through our streets, and breaks into every house almost, where any inhabitants are to be found.
‘Now people fall as thick as leaves from the Trees in Autumn, when they are shaken by a mighty wind.
‘Now there is a dismal solitude in London-streets…Now we could hardly go forth, but we should meet with many Coffins, and see many with sores, and limping in the streets.’
Burial registers show there was a dramatic increase in burials at the New Churchyard, also called the Bedlam burial ground, in Liverpool Street in 1665.
Last year archaeologists unearthed a 7.5 feet wide pit at the site filled with bodies.
Samples were taken from the teeth of some of those found there because the enamel of teeth helps to protect DNA after death.
This means they can serve as time capsules, preserving genetic information that was circulating in an individual’s blood stream at the time of death.
The DNA was sent to experts at the Max Planck Institute for the Science of Human History in Jena, Germany.
In 2014 skeletons excavated during the construction of another part of the Elizabeth line at Farringdon were found to contain traces of DNA from Yersnia pestis.
These individuals are though to have died in Europe’s first major plague epidemic in 1348.
Researchers hope that further analysis of the new DNA may be able to answer questions about the relationship between the 17th Century Great Plague and the 14th Century Black Death.
They say it could also help to reveal whether these plague outbreaks, and other smaller ones around the same time, were part of a single wave or several as a result of trade from Asia.
Previous work on victims in Germany, Spain and Russia has suggested the Black Death and the Great Plague was caused by a single strain of bacterium.
Professor Harding added: ‘The excavation also underlines the strength of custom and order in time of crisis, showing that plague burial, even in mass graves, could be controlled and orderly, with bodies in coffins laid neatly on each other – not quite the shambolic ‘plague pit’ of popular discourse.’
Among the other items found at the site of the mass grave were a headstone, reused in a wall later, which belonged to a plague victim named Mary Godfrey, who died in 1665.
