Plague is a bacterial infection passed by fleas infected with Yersinia pestis, and it is believed to be the agent responsible for pandemics such as the Black Death of the 1300s. Many people are surprised to learn that Yersinia pestis is, in fact, still active in the modern day. The US Centers for Disease Control and Prevention, based in Atlanta, Georgia, document between 1,000 and 2,000 cases of plague each year around the world. Fortunately, modern medical treatments can be used to address the situation and cure the patient, assuming that the infection is caught early enough.
In some parts of the world, plague is considered to be endemic, meaning that it cannot be eradicated. These areas include China, the American Southwest, the Andes mountains, and parts of Africa. Plague has also been documented in other regions, including the Midwest, Russia, and Southeast Asia. In these regions, citizens are advised to be extremely careful around wild animals such as rats, which can carry infected fleas, and to use proper flea control on their pets to avoid bringing the bacteria into the house. In the Midwest especially, several cases each year are linked to domestic cats.
The vast majority of modern plague cases take the classic form of bubonic plague, which causes swollen lymph nodes that are readily apparent to the observer, forming lumps or buboes under the skin. It is accompanied by chills, fever, headache, and general malaise, and can cause death if untreated. Bubonic plague cannot be passed from person to person, however; a carrier animal, such as a flea, must be present in order for someone else to contract the infection. If treated properly with antibiotics, the patient can make a full recovery.
A more unusual form is septicemic plague, which occurs when the bacteria infect the bloodstream directly. It can rapidly spread to internal organs, causing internal bleeding, and it is difficult to diagnose. If left untreated, bubonic plague will turn septicemic as the buboes ulcerate and burst. This form also cannot be passed directly from person to person.
The most dangerous form is pneumonic plague, which infects the lungs, and can be passed from the patient to others as he or she breathes. It is also more virulent than other forms, and patients can die before the classic buboes indicating an infection ever appear. Patients who live in or have visited areas where plague is endemic and present with fever, chills, shortness of breath, and bloody phlegm should be examined for pneumonic plague, to rule it out before moving on to testing for other diseases.