Pneumonic Plague

Pneumonic plague, a severe type of lung infection, is one of three main forms of plague, all of which are caused by the bacterium Yersinia pestis. It is more virulent and rare than bubonic plague. The difference between the versions of plague is simply the location of the infection in the body; the bubonic plague is an infection of the lymphatic system, the pneumonic plague is an infection of the respiratory system, and the septicemic plague is an infection in the blood stream.

Typically, pneumonic form is due to a spread from infection of an initial bubonic form. Primary pneumonic plague results from inhalation of fine infective droplets and can be transmitted from human to human without involvement of fleas or animals. Untreated pneumonic plague has a very high fatality rate.