Caused by the rod-shaped bacterium Yersinia pestis (sometimes categorized as Pasteurella pestis), bubonic plague is an acute and severe infection that occurs mainly in wild rodents, such as rats or squirrels. Two other forms of plague are also caused by Y. pestis: pneumonic plague, in which the lungs are the primary site of infection, and septicemic plague, in which the bloodstream is infected. Plague is a zoonotic disease, which means that it can be transmitted from animals to humans. It can be passed to domestic cats and humans who come in direct contact with the tissues or fluids of infected animals or who are bitten by a flea from an infected animal. It can be passed from person to person via the inhalation of droplets from the cough of a person with pneumonic plague or contact with tissues or fluids from a person infected with plague bacteria. Once infected with plague bacteria, an individual becomes ill within hours or days. The way in which the disease manifests itself depends upon how the individual was exposed to the bacteria. A flea bite or direct contact with infected tissues or fluids may result in bubonic or septicemic plague. Symptoms of bubonic plague include high fever; swollen lymph nodes called buboes, which appear most frequently in the groin area and which give this form of the disease its name; a rash; and changes in blood pressure. Septicemic plague is characterized by fever, chills, severe abdominal pain, shock, and internal bleeding. Inhalation of respiratory droplets from a cat or person whose lungs are infected with plague bacteria can lead to pneumonic plague. Fever, difficulty breathing, a cough producing bloody mucus, headache (often severe), and a rapid heartbeat are common symptoms of pneumonic plague. A person with the bubonic form of the disease may also develop septicemic plague or plague pneumonia. All forms of plague are extremely dangerous and require immediate medical treatment. The plague bacteria cause a massive infection that overwhelms the body's defenses. When plague is untreated, many victims die within a few days. Treatment is with antibiotics such as tetracycline and streptomycin and is begun immediately when infection from plague is suspected (see antibiotic). People are immunized against plague before they travel into areas where plague is endemic, or always present. Control of plague requires the control of wild rodents. Insect repellents are used to protect against flea bites in areas where plague is known to occur. During the 1300s, a pandemic of plague swept across the Eastern Hemisphere, ravaging populations in the Middle East, China, and Europe. Roughly 13 million people in China and 25 million people in Europe—perhaps as much as one third of the population—died from the disease, which was called the Black Death because of the dark color of many victims' faces after death. Although plague still occurs in most of the world, epidemics such as those of earlier centuries have not occurred, thanks to the advent of antibiotics and the vigilance of public health departments in all countries. However, the increased incidence of antibiotic-resistant strains of other bacteria began to worry experts in the 1990s, and in 1995 the first case of antibiotic-resistant plague was documented in Madagascar. By the beginning of the 21st century, security experts were warning of the potential use of plague as an agent of bioterrorism or in biological warfare. (See also chemical and biological terrorism; chemical and biological warfare.) |