Bubonic Plague

Bubonic plague is the disease that is believed to be the cause of the Black Death 1347-1351. The Black Death covered Eurasia and killed more than 237 million people. Bubonic Plague is caused my the Bacteria Yersinia pestis. Y. pestis thrives in rats. It is transmitted to humans through a vector, fleas.

Rat fleas, Xenopsylla cheopis.  who feed on rats infected with Y. pestis take the bacteria into their stomachs. The bacteria while in the flea’s multiply and form a plug to block the stomach of the flea and make it very hungry. The flea being very hungry tries to find many hosts. When it finds a host, a human or another rat or other mammal, it bites the host and tried to suck blood. But the bacteria have blocked its stomach so the flea feels an urge to vomit. The flea vomits and Y. pestis is transmitted to the blood stream of the host. The flea cannot satisfy its hunger and finds more hosts until it dies of starvation.

Once infected, the bacteria infect the Lymph nodes and cause inflammation. This is why it is called bubonic plague because the lymph nodes cause “bubo” or bumps to be formed. The lymph nodes become necrotic, hemmorage and the infection spreads. Bubonic plague commonly results in Acral necrosis which causes bleeding beneath the skin because of hemmoraging. Red blood cells are lying outside of their caplillaries the effected regions turn black and damage tissues. many people believe that this is what the black death is named for. But it is actually named for the figurative sense of black meaning bleak, dreadful and lugubrious for which were the condition experienced by people during the plague.

Bubonic plague shows signs of symptoms 3-7 days after infection. First Symptoms are chills, fever diarrhea headaches and swelling of lymph nodes. If untreated the mortality rate is 30-75%.