A person died in Flagstaff of the rare illness related to the bubonic plague. Once called the “Black Death,” plague is now curable in all its forms if treated quickly.

Septicemic plague occurs if bubonic plague is left untreated, or it can occur directly if the disease enters the bloodstream. Septicemic plague causes bleeding into the organs. The name comes from septicemia, which refers to a serious blood infection.

An Arizona resident died of pneumonic plague, a serious lung infection that requires antibiotics. Here’s what you need to know.