Septicemic plague
 Septicemic plague can cause the blood to form small clots through the body. Without treatment it is almost always fatal. The death rate in medieval times was 99-100 percent. Septicemic plague is the rarest of the three plagues that struck Europe in 1348, the other forms are bubonic and pneumonic plague. In rare cases it can also enter the body through an opening in the skin or by cough from another infected human. In septicemic plague the bacteria grow quickly in the blood, causing severe sepsis.