The Plague of London, 1665
Stephen Usherwood describes how an Asiatic flea, living as a parasite upon black rats, caused as many as 100,000 deaths during the summer and autumn of 1665.
The outbreak of plague in the London area in 1665 was a disaster of the first magnitude, comparable with the Peruvian earthquake or the Bengal cyclone of 1970 in the suddenness of its onset, the size of its death rate and the helplessness of its victims. In a single week at the peak period of the outbreak 7,165 are known to have died of plague, and in the short space of six weeks, August 22nd to September 26th, 32,332.
By December 19th, when the burial registers of the year closed, a total of 97,306 deaths had been registered, and 68,596 of them had been noted as plague deaths. For various reasons the actual number of plague deaths was almost certainly higher than the registers showed, and by the most conservative estimate the outbreak must have cost at least 100,000 lives.