September 16, 2015
2 min read

What is plague?

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

Plague is a serious and potentially fatal bacterial infection caused by the bacteria Yersinia pestis. Humans can contract the disease from the bite of an infected flea. Rodents, including rats, often carry both the plague and the fleas that spread it. While cases of people becoming infected through the handling of carrier animals have occurred, such instances are rare.

The most common type of plague seen throughout history is the bubonic plague, which is an infection of the lymph nodes. Other common types include pneumonic plague, an infection of the lungs, and septicemic, which affects the blood.

Time between infection and the first appearance of symptoms is typically 2 to 8 days. However, pneumonic plague symptoms can appear as soon as 1 day following infection.

Plague symptoms

The symptoms of bubonic plague include:

  • chills;
  • fever;
  • seizures;
  • general feeling of malaise;
  • muscle pain; and
  • the appearance of smooth, painful lymph gland swelling in the groin, armpit or neck areas. The swelling is called a bubo, and is commonly found at the site of the infected flea bite.

If left untreated, about half of those with bubonic plague die.

Symptoms of pneumonic plague include:

  • severe cough;
  • difficulty breathing;
  • fever;
  • frothy, bloody sputum; and
  • chest pain while breathing deeply.

Nearly all cases of pneumonic plague are fatal if left untreated. Unlike other types of plague, individuals with pneumonic plague can spread the infection person-to-person through coughing, which sends tiny droplets carrying the bacteria airborne.

Septicemic plague symptoms include:

  • bleeding due to clotting issues;
  • vomiting;
  • nausea;
  • fever;
  • diarrhea; and
  • abdominal pain.

Septicemic plague can cause death even before any symptoms manifest.


All forms of the plague require immediate treatment, as death can occur as soon as 24 hours after the first symptoms appear.

Antibiotics such as streptomycin, gentamicin, doxycycline or ciprofloxacin are effective in treating the plague. IV fluids, oxygen and respiratory support also assist in treatment.

Due to the risk for person-to-person infection, patients with pneumonic plague require strict isolation – from both caregivers and other patients.


There have been three major, global bubonic plague outbreaks documented throughout history. The first is called the Justinian Plague, named for the Byzantine emperor Justinian I. Starting in 541 AD, the plague swept through much of the Mediterranean basin, killing more than 25 million people.

The second major outbreak is known as the Black Death. A Medieval-period pandemic, it originated in China in 1334. Spreading into Europe, it killed an estimated 60% of the continent’s population.

The third outbreak, often called the Modern Plague, began in China in the 1860s, reaching Hong Kong in 1894. Throughout the next 20 years, it would spread to port cities around the world, causing an estimated 10 million deaths.

However, it was during this time that researchers in Hong Kong identified the bacterium responsible for the disease, leading to the development of a treatment. Doctors in China also discovered that fleas had been the cause of infection, rather than the rodents carrying them.


Cases of plague in the U.S. are rare, although infections have occurred, typically in parts of California, Arizona, Colorado and New Mexico. Currently, more than 95% of the world’s reported cases of plague originate in sub-Saharan Africa and Madagascar.

Additional information: