Thursday 02 August, 2001
Catching The Black Death
The Black Death was the name given to an ancient disease outbreak that swept across Europe and killed as many as three-quarters of the people it infected.
Originally it was thought to be caused by the bubonic plague but this idea is now being challenged as researchers from the UK say that a virus was responsible for the deaths. Science In Action reports.
The Black Death started in Italy in 1347 and during the next three years, it swept across Europe, killing perhaps as many as three-quarters of the people it infected.
At least 25 million people are estimated to have died as the plagues continued for over 300 years until it disappeared in 1670.
It’s been thought that the disease itself was bubonic plague, which is caused by a bacterium carried on the backs of rats. But that idea has been challenged in a book just published in the UK.
Biology Of Plagues
Sue Scott, co-author of the book Biology Of Plagues, was studying records of the outbreak in Penrith, a small town in the north of England, when she began to wonder if the plague theory was mistaken.
She explains why she thinks the rats and its bacterium might not have been the cause after all:
‘In order to have bubonic plague you've got to have appropriate rats and at that time the only rats that were around were black rats … [they] tend to live in areas of human habitation, they tend to be around sea ports and temperate zones.’
‘The only rat that could transmit it up to Penrith would be the brown rat and that didn't appear in this country until 50 years after the plagues disappeared.’
Infectious Disease
Since Scott and her co-author, Chris Duncan, believe that a bacterium was not responsible they looked for the real culprit using a combination of epidemiological, molecular biology and computer modeling.
They took advantage of the fact that all deaths caused by the plagues had to be recorded in the parish register. Scott explains:
‘We looked at the spread through families (because with parish registers they record the burials) and you can put them together as families and see how it spread from person to person, within each household. By doing that we were able to see that it was characteristically a disease spread person to person, it was an infectious disease.’
| ‘You don't have to think in terms of rats and fleas, you think in terms of an infectious disease.’ | |
Old Disease, Modern Methods
By placing the disease in geographical, historical and demographic frameworks, the authors present a new interpretation. Using modern methods to identify an old disease, they then tried to match The Black Death up with a modern equivalent.
They conclude that the closest thing today would be the Ebola and Marburg viruses. These virulent strains are called filo viruses and are the most infectious and lethal viruses known today.
The authors have also looked to the demise of the disease to find a solution to today’s epidemics and in doing so have made comparisons to the HIV virus.
Believing that The Black Death died out because people became resistant to it, Scott cites the partial or complete immunity to the HIV virus identified in people with a mutation of the virus called the CCR-5- Delta-32 mutation.
In the authors view this same mutation may have been responsible for the protection of people against ancient viruses such as The Black Death.
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| Bubonic Plague Facts |
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Caused by Yersina pestis bacteria
Spread by fleas from infected rats
Symptoms include shivering, vomiting and giddiness
World Health Organisation reported 108 deaths from 1,768 cases in 1992
Vaccine available but little use during an epidemic because it requires several weeks to become effective and the immunity lasts less than six months |
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| Black Death |
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The Black Death was so named as sufferers displayed a range of symptoms including the lymph nodes swelling with pus and breaking the blood vessels under the skin.
This caused internal bleeding and turned the skin black. |
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