What Ended the 17th Century Black Death in London: An exploration of the Great Plague of 1665

The Great Plague of 1665 that struck London is often overshadowed by the subsequent Great Fire of 1666, but the reasons for the end of the 17th-century Black Death are equally fascinating. Unlike the bubonic plagues of the 14th and 16th centuries, the 1665 outbreak was widespread and almost everyone knew of its impact. However, exactly what brought an end to the epidemic remains a subject of much debate among historians.

Understanding the Context

The bubonic plague had been endemic throughout the UK since the 1300s, often recurring in approximately 20-year cycles. This phenomenon was ascribed to various factors, such as divine judgment or omens during the reign of monarchs. By the early 17th century, the plague had become a recurring event, with a major outbreak occurring in London in 1665. In the Spring of that year, the first cases were discovered, and by 1666, the city had nearly emptied due to the magnitude of the crisis.

Human Response and the Mechanisms of Spread

Reacting to the epidemic, affluent Londoners fled the city for cleaner, safer country houses and small towns. The King, Charles II, moved to Hampton Court, while Parliament convened in Oxford. Trade and social gatherings were halted, and the poor remained, either succumbing or surviving the disease. It is believed that as the weather grew colder, the numbers of deaths started to decrease. However, the exact reasons for the decline remain unclear.

One theory suggests that people began to develop stronger immunities to the disease. Another theory points to changes in rat behavior. As Charles PanUtilities mentioned, it was believed that the rats, which are carriers of the plague, began to carry the fleas that carried the Yersinia pestis bacteria to other hosts rather than humans. However, the precise mechanism is still debated. Despite these theories, the Great Fire of 1666, though significant, did not significantly impact the plague in the poorer parts of the city where the outbreak was most severe.

The Role of the Great Fire

The Great Fire of London, in 1666, is often misconceived as having ended the plague. However, the fire, though devastating, did not have the widespread impact initially thought. The fire started in the heart of the city and quickly spread, burning many buildings, but it did not reach the poorer districts in the center of London, where the plague was most severe. The fire destroyed much of the city, but it did not provide the end solution that was hoped for. After the fire, the plague reached its peak in the summer of 1666, declined as the weather grew colder, and virtually disappeared thereafter, outside of a minor outbreak in Marseilles in 1710.

Change in Rat Population and the Identification of the Bacterium

The transition from black rats to brown rats was a significant factor in the decline of the plague. It is believed that the black rats, which carried the fleas, were displaced by brown rats, which do not carry the Yersinia pestis bacterium. However, this change in rat population did not occur until about 50 years after the 1665 epidemic. The cause of the plague as Yersinia pestis was not identified until the 19th century. Prior to this, most theories attributed the plague to divine intervention or the presence of miasma (bad air) in the environment.

Final Considerations and Conclusion

As described by Daniel Defoe and other contemporary and modern historians, the end of the Great Plague in 1665 was a culmination of human flight, changes in rat behavior, and natural selection. The fact that two-thirds of Londoners left the city likely played a crucial role in controlling the spread of the disease. The remaining third, primarily the poor and a small group of administrators, experienced a higher mortality rate, but survived as their numbers were significantly reduced. The ultimate end of the plague came as the weather changed, and the immune systems of the survivors adapted to the disease.