Once the flea bites a human, infected blood from the rat is introduced to the healthy blood of the human, and the bacteria spreads. Death occurs in less than a week for humans. A high fever, aching limbs, and fatigue mark the early stages of infection. Eventually, the lymph nodes of the neck, groin, and armpit areas swell and turn black. Those black swellings on victims are what give the Black Death its name. The victim begins to vomit blood and in some instances suffer hysteria from fever and terror. Exposure to any body fluids means exposure to the bacterium, and thus spreading the disease is very easy through coughing victims. The victim dies shortly after the lymph nodes swell until bursting within the body. Within a European village, by the time the initial carrier of the disease had perished, the disease would have already taken early stages in several other individuals, making prevention extreamly difficult.
The Black Death started to spread throughout Asia to Europe and it start to infected humans than about two weeks the humans that been bitten they would start to turn into black and than the next stage the people will start to die but some people say that the Black Death did not start in Asia or Europe it start during china and then it start to spread everywhere.