Bubonic plague is the best-known manifestation of the bacterial disease plague, caused by the bacterium Yersinia pestis (formerly known as Pasteurella pestis). The term "bubonic plague" is often used synonymously for plague, but it does in fact refer specifically to an infection that enters through the skin and travels through the lymphatics, as is often seen in flea-borne infections. Bubonic plague kills about 50% of infected patients in 4-7 days without treatment, and is believed by many to be the Black Death that swept through Europe in the 1340s, killing millions of people.
The bubonic plague is an infection of the lymphatic system, usually resulting from the bite of an infected flea. The fleas are often found on rodents, such as rats, and seek out other prey when their rodent hosts die. Once established, bacteria rapidly spread to the lymph nodes and multiply. Yersinia pestis can resist phagocytosis and even reproduce inside phagocytes and kill them. As the disease progresses, the lymph nodes can hemorrhage and become necrotic. Bubonic plague can progress to lethal septicemic plague in some cases. The plague is also known to spread to the lungs and become the disease known as the pneumonic plague.
The most famous symptom of bubonic plague is swollen lymph glands, called bubouls. These are commonly found in the armpits, groin or neck. The bubonic plague was the first step of the ongoing plague. Two other forms of the plague, pneumonic and septicemic, resulted after a patient with the bubonic plague developed pneumonia or blood poisoning.
Other symptoms include spots on the skin that are red at first and then turn black, heavy breathing, continuous blood vomiting, aching limbs and terrible pain. The pain is usually caused by the actual decaying, or decomposing of the skin while the infected person is still alive. When death begins the person will get spasms.
See main article: Black Death. The deadly disease has claimed nearly 200 million lives (although there is some debate as to whether all of the plagues attributed to it are in fact the same disease). The first recorded epidemic ravaged the Byzantine Empire during the sixth century, and was named the Plague of Justinian after emperor Justinian I, who was infected but survived. The most infamous and devastating instance of the plague was the Black Death, which killed a quarter to half of the population of Europe. The Black Death is thought to have originated in the Gobi Desert. Carried by the fleas on rats, it spread along trade routes and reached the Crimea in 1346. In 1347 it spread to Constantinople and then Alexandria, killing thousands every day, and soon arrived in Western Europe.
The next few centuries were marked by several local outbreaks of lesser severity. The Great Plague of London, 1665–1666, was the last major outbreak of the bubonic plague in Europe. The plague resurfaced in the mid-18th century; like the Black Death, the Third Pandemic began in Central Asia. It spread worldwide, killing millions, into the early 20th century.
During the Second Sino-Japanese War, plague was used as a bacteriological weapon by the Imperial Japanese Army. These weapons were provided by Shirō Ishii's units and used in experiments on humans before being used on the field. For example, in 1940, the Imperial Japanese Army Air Service bombed Ningbo with fleas carrying the bubonic plague. During the Khabarovsk War Crime Trials the accused, such as Major General Kiyashi Kawashima, testified that, in 1941, some 40 members of Unit 731 air-dropped plague-contaminated fleas on Changde. These operations caused epidemic plague outbreaks.
In modern times, several classes of antibiotics are effective in treating bubonic plague. These include the aminoglycosides streptomycin and gentamicin, the tetracyclines tetracycline and doxycycline and the fluoroquinolone ciprofloxacin. Patients with plague in the modern era usually recover completely with prompt diagnosis and treatment.