ABSTRACT
Early cities were characterized by a great variety of building and housing structures, some of very poor quality and others poorly located. Bubonic plague is spread from person to person by bites of infected fleas, which are external parasites of rats and other animals that successfully adapted to urban environments. Early signs of cities and an urbanization of society were evident around 4000 to 3500 bc in Mesopotamia, along the Tigris and Euphrates rivers and their tributaries. The peoples of Mesoamerica, such as the Maya, Zapotecs and Aztecs, also developed major urban communities. In these Mayan urban centers mathematics and astronomy flourished. The impact of the industrial revolution on the urbanization of Western Europe was dramatic. The urban environment provided a concentration of acceptable food resources and harborage for insect and rodent populations, which were able to increase and persist throughout the year.
