20.2 Plague Example

The etiology of plague is a bacteria known as Yersinia pestis a gram-negative rod (6). There is some question as to whether or not the bacteria now endemic to the American Southwest is the same as the historical cause of the bubonic plague in 1334 that killed off more than 20 million people in Europe (7). Of course, there have been multiple epidemics throughout history as a result of plague, but this is the most notable example. The organism, Y. pestis, was discovered in 1894 (8). Regardless of this, plague as we know it in the southwest is very real and very deadly. Y. pestis is an organism that can easily adapt to a wide variety of host organisms, which makes it ideal as a harbinger of an epidemic. There are three forms of plague. First is pneumonic plague, which is spread by aerosolized droplets and presents as a type of pneumonia. This form of plague has a near 100% mortality. The affected person develops a lobar pneumonia, which leads to necrosis and death. Without rapid administration of antibiotics, the affected person will die within 18–24 h of onset. Second is bubonic plague. Typically, this presents with lymphadenopathy, and then, in 2–3 days, the patient develops chills, fever, and fatigue. On the seventh day, the affected person develops buboes. Buboes are nonfluctuant, warm, and tender. After the administration of antibiotics, these resolve after approximately 5 days. Third is septicemic plague. This is bacteremia secondary to rapidly replicating Y. pestis. This results in an overwhelming sepsis, leading to shock and disseminated intravascular coagulation (DIC). As a weapon, plague is a poor agent. There are numerous, commonly used antibiotics that will effectively treat plague. Plague has persisted despite human efforts because it is transmitted primarily by fleas. Fleas can transmit the disease to rodents, and rodents then carry the disease across a broad area and tend to congregate near humans. Public health officials typically monitor plague by identifying large numbers of rodents die off quickly and collecting samples in and around their burrows. There is no current vaccination against plague.