Plague — what it is

Overview

Plague is caused by the bacterium Yersinia pestis, which circulates in wild rodents and their fleas in many parts of the world, including natural-focus regions of the former Soviet Union, Africa, Asia and the Americas.

Human cases are now rare, and most are treatable when diagnosed promptly. The main clinical forms are bubonic plague, septicemic plague and pneumonic plague.

Symptoms

General symptoms can include sudden fever and chills, headache, weakness and muscle aches.

Bubonic plague typically causes painful, swollen lymph nodes (buboes), often in the groin, armpit or neck.

Pneumonic plague affects the lungs and can cause shortness of breath, chest pain, and a cough — sometimes with blood-tinged sputum. It is the most serious form.

How it spreads

Most cases result from the bite of an infected flea, or from handling infected animals.

Pneumonic plague is the only form that can spread between people, through infectious respiratory droplets. This requires close contact with a sick person.

Treatment & prevention

Plague is treatable with common antibiotics and is far more likely to respond well when treatment begins early.

Prevention focuses on reducing flea exposure, avoiding sick or dead animals, and using protective precautions. There is currently no widely used plague vaccine for routine public use.

About the current Irkutsk event

The Irkutsk case tracked on this site is being investigated as pneumonia of unknown cause. Russian authorities have not confirmed plague. See the Irkutsk event page for the current status.