Why a global outbreak of pneumonic plague is unlikely

The bubonic plague is the most common variant and is spread by the bites of infected fleas. Once inside a human host, the bacterium travels to the lymph nodes where it causes painful sores called ‘buboes’ in the groin, neck and armpits. Human-to-human transmission of bubonic plague is rare, but the bacterium can spread to the blood where it causes septicaemic plague, or the lungs, causing pneumonic plague.