What is Plague?

Plague is a disease caused by the Yersinia pestis bacterium. There are three major types: bubonic plague (lymph node infection), septicemic plague (blood infection), and pneumonic plague (lung infection). 

Plague continues to be a threat because of vast areas of persistent wild rodent infection.

How do you get Plague?

Plague is transmitted through bites from infected rodent fleas. Other transmission methods are less common. Plague can be transmitted by inhaling respiratory droplets from infected cats, dogs, or patients with pulmonary (pneumonic) plague when they cough or sneeze droplets into the air.

Susceptibility and Resistance

Immunity after recovering from plague is variable and depends to some extent on the amount of plague bacteria to which the person is exposed again. If large numbers of bacteria enter the body, prior infection may not always protect against re-infection.

Incubation Period

The incubation period for Plague is 1-7 days.

What are the Symptoms?

Initial symptoms include non-specific signs such as fever, chills, general fatigue, muscle fatigue, nausea, sore throat and headache. In the case of bubonic plague, the lymph nodes that drain the site of the flea bite will swell, become painful and enlarge sometimes to the size of a grapes or small limes.  They often rupture through the skin and discharge pus. Untreated bubonic plague has a case-fatality rate of about 50-60 percent.

Pneumonic plague is characterized by pneumonia in the lungs and possible inflammation in the chest or excess fluid accumulating in the chest cavity.

All forms of plague may progress to septicemic plague where the infection spreads through the bloodstream to other parts of the body, including the meninges (the protective linings of the brain). Abnormal blood clotting and severe shock may occur.

Untreated pneumonic and septicemic plague are invariably fatal.

Preventative Measures

There is no vaccine available for plague. The best preventive measures are to avoid contact with fleas and potentially infected rodents and other wildlife.  In the event of exposure to the flea bites when an outbreak in in progress, antibiotics are given to people who have been exposed before they become sick.


Plague is often misdiagnosed, especially in travellers who develop the illness after returning from an endemic area. Several classes of antibiotics are effective in treating plague. If diagnosed with plague, the patient must be isolated. The patient and their belongings must be completely rid of fleas using an insecticide effective against local fleas and safe for humans. For patients with pneumonic plague, strict isolation is necessary to prevent airborne spread until appropriate antibiotic therapy is completed and for at least 48 hours after.


Where Does It Commonly Occur?

Wild rodent plague exists in the western half of the USA, large areas of South America (Brazil, Peru, Ecuador and Bolivia), north central, eastern and southern Africa, southeastern Europe near the Caspian Sea, and central and southeast Asia (China, Laos, Mongolia, Myanmar, India and in Vietnam).