In cases of primary pulmonary plague, patients become infected by inhaling bacteria-rich aerosols produced by individuals who developed secondary pneumonia in the course of plague severe blood infection.
V primerih primarne pljučne kuge se bolniki okužijo z vdihavanjem aerosolov z veliko količino bakterij, ki jih tvorijo osebe, pri katerih se je med kugo s hudo okužbo krvi (septikemično kugo) razvila sekundarna pljučnica.