a highly infectious disease caused by the Yersinia pestis bacteria, which is most commonly transmitted to humans by fleas from infected rats

Where and when plague first affected humans is not known, but the first recorded epidemic of plague occurred in Athens in 430 B.C., and an outbreak in Rome in 262 A.D. is recorded to have killed as many as 5,000 people a day.

In the early 1330's an outbreak of plague occurred in China. Since China was one of the busiest of the world's trading nations, it was only a matter of time before the outbreak spread to western Asia and Europe. In October of 1347, several Italian merchant ships returned from a trip to the Black Sea. When the ships docked in Sicily, many of those on board were already dying of plague. Within days the disease spread to the city and into the surrounding countryside. By the following August, the plague had spread as far north as England, where people called it "The Black Death" because of the black spots it produced on the skin. In winter the disease seemed to disappear, but only because fleas -- which carry it from person to person -- are dormant then. Each spring, the plague attacked again, killing new victims. After five years, an estimated 25 million people were dead, one-third of Europe's population at the time.

Although a widespread plague epidemic has not struck the world since the 1300's, the disease is still found in many parts of the world. And, while plague is far more common in underdeveloped areas, cases still can and do appear in well-developed areas, including Europe and the United States.

About the Disease

The three most common forms of the disease are bubonic plague, pneumonic plague, and septicemic plague.

Bubonic plague symptoms usually appear 2 to 5 days after exposure to the bacteria. Chills and fever, muscle pain, and a general ill feeling are quickly followed by smooth, painful lymph gland swelling called a bubo. That swelling is commonly found in the groin, but may appear in the armpits or neck, most often at the site of the original infection (bite or scratch). While bubonic plague can be transmitted from person to person, direct contact with either an infected person or infected bodily fluids is usually required, making full-blown epidemics fairly easy to avoid.

lymph node swelling caused by Bubonic plague

Pneumonic plague symptoms can appear as quickly as one day after exposure and include severe cough, difficulty breathing, fever, and bloody sputum. When someone with pneumonic plague coughs, tiny droplets carrying the bacteria move through the air. Anyone who breathes in these particles may catch the disease. An epidemic may be easily started this way, especially since the infected person may initially believe he/she is suffering from little more than a nasty cold and not take necessary precautions to avoid spreading the disease.

Septicemic plague may cause death even before its characteristic symptoms appear. Those symptoms are tiny blood clots under the skin that cause tissue death, which in turns causes the tissue to turn black. It was this form of plague that struck Europe in the 1300's, which is why that particular outbreak of plague has become known as the "Black Death."

Although all three forms of plague can be treated with antibiotics (usually streptomycin, chloramphenicol, and tetracycline), that treatment must begin within 24 hours of first symptom appearance in order for the patient to have a better than 50-50 chance of survival. A vaccine against bubonic plague was developed by Dr. Waldemar Haffkine in 1897, but no vaccine against the other two forms has yet been found.

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This page was last updated on 06/11/2017.