Yersinia pestis

Yersinia pestis is a bacterium that causes plague, a zoonotic infection that affects humans and animals. It is usually transmitted through the bites of infected fleas, direct contact with infected animals, or by inhalation of respiratory droplets from person to person in cases of pneumonic plague.

History

Yersinia pestis has been responsible for several major pandemics throughout history, including the Black Death, which occurred in Europe in the 14th century and is estimated to have killed between 75 million and 200 million people. The bacterium was first identified by Alexandre Yersin in 1894 during an outbreak of plague in Hong Kong.

Transmission

Yersinia pestis is typically transmitted through the bites of infected fleas, which live on rodents and other small mammals. When an infected flea bites a human or animal, it regurgitates the bacteria into the wound, causing infection. The bacterium can also be transmitted through direct contact with infected animals, such as handling or dissecting them, or by inhalation of respiratory droplets from person to person in cases of pneumonic plague.

Symptoms

The symptoms of Yersinia pestis infection vary depending on the form of the disease. There are three main forms: bubonic, septicemic, and pneumonic. Bubonic plague is characterized by swollen lymph nodes, or "buboes," in the groin, armpits, or neck, as well as fever, chills, and weakness. Septicemic plague occurs when the bacteria enter the bloodstream directly and cause a severe infection, which can lead to organ failure and death if left untreated. Pneumonic plague is the most deadly form of the disease and occurs when the bacteria infect the lungs, causing pneumonia.

Treatment

Yersinia pestis infections are typically treated with antibiotics, such as streptomycin or gentamicin, which are effective against the bacterium. Treatment should be started as soon as possible after symptoms appear to reduce the risk of complications and death. In addition to antibiotic treatment, patients may also require supportive care, such as oxygen therapy and fluid replacement, to manage symptoms and prevent organ failure.

Prevention

Prevention of Yersinia pestis infection involves avoiding contact with infected fleas, animals, and people. This can be achieved by wearing protective clothing, using insecticides to control flea populations, and avoiding handling or dissecting infected animals. Vaccines are also available for people who work with the bacterium in laboratory settings or who are at high risk of exposure.