It was transferred by mice, 1,000's of mice and it did not stop until the huge london fires that killed most of the mice.
(Hey, it's as reasonable as any of the rest of this wild speculation here.)
You're thinking of the Great London Plague of 1664-1665, which is generally considered to have been halted by the London Fire of 1666 (though the number of infected and deaths had already begun a steep decline). The Black Death was in the 1340s.