Fear not, for the CDC also states that "Plague is infamous for killing millions of people in Europe during the Middle Ages.

Pneumonic plague is a form of plague that results from Yersinia pestis infection. This article explores its causes, symptoms, and treatment in more detail.

Pneumonic plague is the most deadly and easiest to spread, with a nearly 100% fatality rate untreated, said Lisa Morici, a microbiologist and immunologist in the Tulane University School of Medicine.

Pneumonic plague is the most deadly and easiest to spread, with a nearly 100% fatality rate untreated, said Lisa Morici, a microbiologist and immunologist at the Tulane University School of Medicine.

Pneumonic plague can also occur when the bacteria from untreated bubonic or septicemic plague spreads to the lungs. Septicemic plague doesn’t spread from person to person.

Pneumonic plague infected the lungs after inhaling aerosolized bacteria and septicaemic is when the bacteria infects the blood through direct exposure or via lungs or lymphatic system.

The pneumonic plague is often deadly and can be transmitted from person to person. However, Dr. Fawcett says it's not clear if that happened.

What Is Plague? There are three forms of plague in humans: bubonic, septicemic and pneumonic, with bubonic having the lowest risk of death and pneumonic the highest.