PNEUMONIC PESTE Inhalation of the gram-negative bacterium Yersinia pestis ( Y . pestis). Humans usually acquire it because of flea bites. There are three types of plague: bubonic, pneumonic and septic. Primary pneumonics occurs when it affects the respiratory area without having the attributes of bubonics; secondary pneumonic plague is the one that occurs after bubonics have contracted; septisémic plague is produced by late treatment of plague with septic shock and other pathologies, with mortality being around 100%.