The Great Plague was a massive outbreak of disease in Britain that killed 60,000 people, up to a fifth of London's population in 1665. It is generally believed to have been bubonic plague, an infection by the bacterium Yersinia pestis transmitted via a rat vector. Other infectious agents have also been suggested such as septicemic plague and pneumonic plague.
Accounts of the plague were given by Daniel Defoe in A Journal of the Plague Year, and by Samuel Pepys in his famous diary.
The first recorded victim of the 1665 plague was Margaret Porteous on April 12, however as the poor were generally hit first it is likely that she was not the first actual victim. The Great Fire of London in 1666 killed most of the London rats therefore wiping out the plague, and the 16 human deaths in the fire were probably fewer than would have occurred had the fire not happened.
Though concentrated in London, the outbreak affected other areas of the country. Perhaps the most famous example was the village of Eyam in Derbyshire. The plague arrived in a parcel of cloth sent from London. The villagers imposed a quarantine on themselves to stop the further spread of the disease. Though successful, the village lost around 80% of its inhabitants.
The 1665 epidemic was in fact on a far smaller scale than the earlier "Black Death", a virulent outbreak of disease in Europe between 1347 and 1353, but was remembered afterwards as the "great" plague because it was one of the last widespread outbreaks in Europe.