<P> The three types of plague are the result of the route of infection : bubonic plague , septicemic plague , and pneumonic plague . Bubonic plague is mainly spread by infected fleas from small animals . It may also result from exposure to the body fluids from a dead plague - infected animal . In the bubonic form of plague , the bacteria enter through the skin through a flea bite and travel via the lymphatic vessels to a lymph node , causing it to swell . Diagnosis is made by finding the bacteria in the blood , sputum , or fluid from lymph nodes . </P>
where does the germ that causes bubonic plague normally live in nature
fleas from small animals