A mystery has surrounded the true cause of The Great Plague of London in 1665. The Black Death” was the last major plague to hit the UK but has left an indelible mark on the country’s history.

After all, this insidious outbreak killed off 100,000 Londoners, one-quarter of the city’s population in 18 months. The bubonic plague Spread by fleas, it was highly contagious and few who were affected survived. Theirs was an agonizing death with severe headache, vomiting, inflamed glands in the groin, inflamed tongue and the victim’s skin turned black in patches.

Vanessa Harding, Professor of London History at Birkbeck, University of London says of Londoners at the time,

Not many people who actually got it survive but some do. And it seems to be quite easily transferred from person to person even if we’re not sure currently about the agency or way in which this actually happens. But there are also what we might consider public health measures , which from their point of view include killing cats and dogs, getting rid of beggars on the streets, trying to cleanse the city in both moral and practical terms. The people who do best are those who get out of London.

Dead men (and women) do tell tales. Excavation on a rail line on the Crossrail site, at the Bedlam Burial Ground (New Churchyard) at Liverpool Street in East London has unearthed evidence of the fatal pathogen. Neatly buried coffins and a mass grave, totaling 3,500 skeletal remains were unearthed by archaeologists.

Alison Telfer from the Museum of London Archaeology (Mola) says,

We found about three-and-a-half thousand burials at this site. We’ve been working here for the last fine-and-a-half years on and off and we’re hoping we’ll be able to get positive identification of this plague on a number of individuals.

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Analyzing the skeletons from the Crossrail dig.

The search for the definitive cause of the plague involved gathering the skeletons from the dig, a process that continued last year. The skeletons were taken to the osteology department at Mola, where they are stored.

Michael Henderson began examining the skeletons for clues. He explains,

They’re carefully boxed, individual elements, legs separately, arms separately, the skulls and torsos. We excavated in the region and three and a half thousand skeletons, one of the largest archaeologically excavated to this date. A vast data set that can give us really meaningful information.

The bones were laid out in anatomical order and the teeth were removed. Henderson adds,

The best thing to sample for DNA is the teeth; they’re like an isolated time capsule.

Tooth enamel preserves the genetic information of any bacteria that was circulating in the individual’s bloodstream at the time off death. Stable isotope analysis of strontrium and oxygen, for example, can tell the scientists if the victims were native Londoners or visitors. Carbon and nitrogen isotopes can reveal whether the victims ate meat, vegetables or seafood. Microbiome DNA reveals the amount of airborne particles and pollutants they breathed.

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DNA from the London dig being analyzed in Germany.

The teeth were sent for ancient DNA analysis to the Max Planck Institute for the Science of Human History in Jena, Germany. At the Institute, molecular palaeopathologist Kirsten Bos drilled out the tooth pulp to search for 17th century bacteria. She found five positive results from 20 individuals tested. She says,

We could clearly find preserved DNA signatures in the DNA extract we made from the pulp chamber and from that we were able to determine that Yersinia pestis was circulating in that individual at the time of death.

We don’t know why The Great Plague was the last major plague in the UK and whether there were genetic differences in the past, those strains that were circulating in Europe to those circulating today; these are all things we’re trying to address by assembling more genetic information from ancient organisms.

Scientists hope to learn more about the victims, the bacterial cause and the spread of plague.

Don Walker, senior osteologist at Mola says,

It (the plague) does not behave that way today. It’s much slower and spreads less dramatically. Could it be that there was some form of mutation? Or was it to do with host susceptibility and response? Were humans carrying greater disease loads in those days (eg, tuburculosis) and had poor nutrition made them more vulnerable?

We want to know if there was a local/European plague focus – a reservoir of the disease within a rodent population – or were there separate waves of plague coming from Asia. Current evidence suggests the former.

This year marks the 35oth anniversary of the Great Fire of London, which is thought to have stopped the plague.

By he way, have no fear that the bubonic plague has been resurrected during the excavation and analysis. The plagues does not survive in the ground.

Nancy Loyan Schuemann

Nancy Loyan Schuemann is a writer specializing in architecture, safes, profiles, histories and a multi-published fiction and non-fiction author and is Nailah, Middle Eastern dancer.

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