The Black Death was caused by the bacterium Pasteurella pestis, transmitted by the fleas on rats. It ravaged Europe in the 14th century, killing about one third of the population, having started in China. It came to England, when a ship from Calais landed at Melcombe Regis in Dorset in 1348.
I also read that it came over here from traders (i think) in another country & the disease then travelled all over the country in the form of fleas that carried it, they were carried by rats & then the fleas started biting humans, giving them the disease. xx