Actually, it never left. At least not in Madagascar, where plague is endemic, and is reported every year in the area. In fact, they even have a plague season. It runs from September through April, and they usually get about 400 cases each year. However, according the WHO “the ongoing pneumonic plague event has been reported in a non-endemic area and in densely populated cities for the first time.” There have already been more then 300 cases and 40 deaths in Madagascar and plague season is just getting started.
Usually, bubonic plague is the more common form in this area, and is transmitted via fleas. Pneumonic plague, which effects the lungs, is airborne, and is therefore more easily spread and more deadly. If left untreated, bubonic plague travels to the lungs and becomes pneumonic plague. Without antibiotics, pneumonic plague is 100% fatal. The WHO is working on distributing more antibiotics, but for a disease that’s spread via the air and has reached a densely populated area, they are facing a complicated race against time.