In 1665 and 1666, a city experienced two enormous tragedies: the Great Plague in London and the Great Fire in London. The plague killed around 15-20% of the city’s population, while the fire burned about a quarter of the metropolis of London, leaving around 100,000 people homeless. And although the city only officially recorded a small number of fire deaths, the actual number of deaths was probably quite high.
Humans often want to find a silver lining in the midst of a disaster, and a myth that has arisen around these twin tragedies is that the great fire ended the great plague by chasing away the rats that spread the disease.
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“I was raised with this myth,” says Adrian Tinniswood, senior researcher in history at the University of Buckingham, England, and author of By heaven’s permission: the story of the great fire. “It was the kind of standard school speech in the 60s when I was young.”
The great plague from 1665 to 1666
The Great Plague was the last major plague epidemic in London, a bacterial infection caused by Yersinia pestis. The epidemic began in late winter or early spring 1665. By the time King Charles II fled the city in July, the plague was killing about 1,000 people a week. The death rate peaked in September when 7,165 people died within a week.
Officially, the city has recorded 68,596 deaths from the Great Plague, and the actual death toll may have exceeded 100,000. Most of these deaths were due to bubonic plague, a form of plague that spread by fleas on small mammals. In London, the main carriers were rats. (In the United States, where the plague has probably existed for a The 1900 epidemic in San Francisco, squirrels and prairie dogs can and do transmit the plague to humans.)
After peaking in September 1665, deaths from the plague in the city began to decrease that winter. In February 1666, King Charles II returned to London, reporting a belief that the city had become “reasonably safe,” says Christoph Heyl, president of British literature and culture at the University of Duisburg-Essen, Germany, who wrote about the great fire.
So, although London continued to report plague victims until 1679, the main epidemic ended mainly on September 2, 1666, the night when a baker by the name of Thomas Farriner had unintentionally started the great London fire.
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The great fire of 1666
“In a world lit only by fire, people always set fire to their homes,” says Tinniswood of England in the mid-1600s. What was more unusual was that someone would light a house fire that set fire to more than 13,000 other homes – which Farriner accidentally did.
The great fire destroyed most of the official city of London (which was geographically smaller than London today), but it did not reach many of the outer metropolitan areas like Whitechapel, Clerkenwell and Southwark which were also affected by the plague. This means that while the fire chased rats out of the 436 acres it burned, it did not spread far enough to hunt all of the rats that spread plague in Greater London.
The plague was in decline as the fires started
In fact, the data suggests that the fire had no effect on the plague. Deaths from the plague in London were already down at the time of the fire, and people also continued to die from the plague after the fire. It is not known exactly when people started to say that the fire had ended the plague, because people did not seem to believe it at the time.
“If you look at the speech at the time, there was never a connection between the end of the plague and Great Fire,” says Heyl. As an example, he points to a piece of royalist propaganda which attempted to run the Great Fire as a kind of political success for King Charles II. “Even in a text like this, there is no trace of a link between the fire and the end of the plague.”
The uncomfortable fact is that historians don’t really know why the Great Plague ended. After the fire, London reinforced the old building codes which favored brick over wood because it is less flammable. Brick is also more difficult to dig for rats, but as London Museum curator Meriel Jeater notes that there has been no concomitant hygienic or sanitary improvement with this use of brick that could have explained an eradication of the plague.
Even in the 21st century, the plague remains a serious disease. Between August and November 2017, a a plague epidemic in Madagascar resulted in 2,417 infections and 209 deaths. Antibiotic treatment is extremely effective against the plague. But when the disease is not diagnosed or antibiotics are not available, it can still be very fatal, as it was in 1665 and 1666.