Plague (disease)

Plague
Yersinia pestis seen at 200× magnification with a fluorescent label.
Specialty	Infectious disease
Symptoms	Fever, weakness, headache[1]
Usual onset	1–7 days after exposure[2]
Types	Bubonic plague, septicemic plague, pneumonic plague[1]
Causes	Yersinia pestis[2]
Diagnostic method	Finding the bacterium in a lymph node, blood, sputum[2]
Prevention	Plague vaccine[2]
Treatment	Antibiotics and supportive care[2]
Medication	Gentamicin and a fluoroquinolone[3]
Prognosis	≈10% risk of death (with treatment)[4]
Frequency	≈600 cases a year[2]

Plague is an infectious disease caused by the bacterium Yersinia pestis.^[2] Symptoms include fever, weakness and headache.^[1] Usually this begins one to seven days after exposure.^[2] There are three forms of plague, each affecting a different part of the body and causing associated symptoms. Pneumonic plague infects the lungs, causing shortness of breath, coughing and chest pain; bubonic plague affects the lymph nodes, making them swell; and septicemic plague infects the blood and can cause tissues to turn black and die.^[2][1]

The bubonic and septicemic forms are generally spread by flea bites or handling an infected animal,^[1] whereas pneumonic plague is generally spread between people through the air via infectious droplets.^[1] Diagnosis is typically by finding the bacterium in fluid from a lymph node, blood or sputum.^[2]

Those at high risk may be vaccinated.^[2] Those exposed to a case of pneumonic plague may be treated with preventive medication.^[2] If infected, treatment is with antibiotics and supportive care.^[2] Typically antibiotics include a combination of gentamicin and a fluoroquinolone.^[3] The risk of death with treatment is about 10% while without it is about 70%.^[4]

Globally, about 600 cases are reported a year.^[2] In 2017, the countries with the most cases include the Democratic Republic of the Congo, Madagascar and Peru.^[2] In the United States, infections occasionally occur in rural areas, where the bacteria are believed to circulate among rodents.^[5] It has historically occurred in large outbreaks, with the best known being the Black Death in the 14th century, which resulted in more than 50 million deaths in Europe.^[2]