Plague - a disease known since ancient times, the first possible information about her fall at the end of II and the beginning of III centuries BC. Known is the so-called "Plague of Justinian" (551-580), which originated in the Eastern Roman Empire and covered the entire Middle East.
By the epidemic killed more than 20 million people. In the X century was a great plague in Europe, especially in Poland and Kievan Rus. In 1090 in Kiev for two weeks from the plague killed more than 10,000 people. In the XII century plague arose several times among the Crusaders. In the XIII century in Poland and Russia were several explosions plague. In the XIV century Europe walked terrible epidemic of "Black Death", inscribed in East China.
In 1348 she died of nearly 15 million people, accounting for a quarter of the entire population of Europe. In 1346 the plague was entered in the Crimea, and in 1351 in Poland and Russia. In the future, in Russia there were outbreaks of plague in 1603, 1654, 1738-1740 and 1769. The epidemic of bubonic plague swept through London in 1664-1665 years, killing more than 20% of the population. The last case of bubonic plague infection was recorded in 2002 in the United States.
In the Middle Ages contributed to the spread of the plague unsanitary conditions that prevailed in the cities. Sewage was not, and all the scum flowed directly along the streets, which served as an ideal environment for the life of rats. Alberti described the Siena, which "loses much ... due to lack of cloaca.
That is why the whole city publishes stench, not only in the first and last night in custody when the vessels with accumulated filth poured through the windows, but also in other hours is disgusting and highly zagreznёn ". In addition, in many places the cause of the plague announced cats ostensibly a servant of the devil and infect humans.
Mass extermination of cats led to an even greater increase in the number of rats. The cause of the infection often are flea bites, which have previously lived in infected rats.