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Symptoms and Signs of Plague Disease (Black Death)

Doctor's Notes on Plague Disease (Black Death)

Plague (also called “Black Death”) is an infectious disease caused by plague bacillus (bacterium), Yersinia pestis. It spreads easily and can be fatal if not treated. The plague killed nearly 200 million people during the Middle Ages and more recently there is concern that forms of the plague could be used as biological weapons in a bioterrorism attack.

Symptoms of plague include fever, chills, body aches, sore throat, headache, weakness, general feeling of illness, abdominal pain (may be the only symptom for septicemic plague), nausea, vomiting (may be bloody), constipation, diarrhea, black or tarry stools, cough (may contain blood), shortness of breath, stiff neck, fever, heart irregularities, low blood pressure, confusion, seizures (later in the infection period), buboes (enlarged, tender, swollen lymph gland most commonly found in the groin, under the arms, or on the neck, depending on the locations of the flea bite), and bleeding into the tissues that can turn tissue black.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/11/2019

Plague Disease (Black Death) Symptoms

  • Common plague symptoms include:
  • Bubo: This is an enlarged, tender, swollen lymph gland most commonly found in the groin, under the arms, or on the neck, depending on the locations of the flea bite.
  • Skin: Bleeding into the tissues can turn tissue black. The medieval name black death is thought to have originated from the deeply darkened skin, bleeding, vomiting blood, and tissue death associated with septicemic and pneumonic plague. The initially rose-colored lesions most likely inspired the child's nursery rhyme "Ring Around the Rosy."
    • "Ring around the rosy" -- rose-colored areas of skin
    • "Pocket full of posies" -- sweet-smelling flowers that those tending the sick would carry to ward off the stench of disease
    • "Ashes, ashes" -- impending death (or "A-choo, a-choo" -- The sneezing and coughing of those with pneumonic plague)
    • "All fall down" -- death

Plague Disease (Black Death) Causes

The bacterium (Yersinia pestis) that cause plague can be transmitted from a host such as a rat to a human through the bite of an animal or insect (such as a flea). These bites transport the zoonotic disease. The animal or insect that spreads the disease is referred to as a vector. More than 200 different rodents and other species can serve as hosts. Hosts can include domestic cats and dogs, squirrels, chipmunks, marmots, deer mice, rabbits, hares, rock squirrels, camels, sheep, and other animals.

The vector is usually the rat flea. Thirty different flea species have been identified as vectors of the plague. Other vectors of plague include ticks and human lice. Transmission can also occur when someone inhales plague-infected organisms that have been released into the air. Plague can be aerosolized, as in acts of terrorism, causing the inhalation (pneumonic) form of the disease. People infected with pneumonic plague can also transmit airborne plague through coughed droplets of their own respiratory fluid. Close contact with plague-infected tissue or fluid can also transmit plague-causing bacteria to humans.

  • Types of plague:
    • Bubonic plague: The bacteria that cause plague can thrive and grow in the flea's esophagus. This crowding of bacterial growth prevents food from entering the flea's stomach. To overcome starvation, the flea begins a blood-sucking rampage. Struggling to swallow, the flea vomits the plague-causing bacteria into the victim's skin during a bite. The germs invade nearby lymph glands in the bitten animal and produce an inflamed lymph node called a bubo. The plague spreads along the lymph system to every organ. In rare cases, plague spreads to the covering of the brain. Severe illness follows. Bubonic plague has a 13% death rate in treated cases and a 50%-60% death rate if left untreated. Bubonic plague is the most common form of plague.
    • Pneumonic plague: Direct inhalation of the plague-causing germs results in pneumonic plague. Severe illness follows. The death rate for the pneumonic form of plague is 100% if not treated within the first 24 hours of infection. Plague bacteria may be released into the air as a weapon of biological warfare or terrorism causing this type of the disease, or plague may be transmitted person to person through the inhalation of droplets coughed from the lungs of a person with pneumonic plague. Transmission through direct contact is rare.
    • Septicemic plague: This form of serious disease may occur quickly and causes severe blood infection throughout the body (primary). It is difficult to diagnose early because there are no buboes or lung abnormalities. This type of plague can also develop from one of the other types of plague (secondary). Septicemic plague has a 40% death rate in treated cases and about 100% in untreated cases.
  • Risk factors: The following conditions may increase the likelihood of a person contracting a plague infection.
    • Living in a rural area, especially in areas where plague is common
    • Having contact with sick animals, dead animals, small rodents, or other possible hosts
    • Participating in wilderness activities (such as camping, hiking, sleeping on the ground, hunting)
    • Exposure to flea bites
    • Exposure to naturally occurring plague in the community
    • Employment as a veterinarian
    • Outdoor activity during the summer months
  • Travel: Anyone who has traveled recently in the southwestern and Pacific Coast regions of the U.S., particularly in New Mexico, Arizona, California, and Utah, might have had a flea bite. Although contracting plague while visiting another country is rare, doctors may suspect that a flea might have bitten a patient with plague-like symptoms who have recently traveled abroad to areas where plague is present.
  • Animal contact: Close contact with infected animals and travel through rural areas are risk factors for contracting plague. Historically, rats have been the principal hosts of the plague. Currently in the U.S., ground and rock squirrels are the most common hosts. In recent years, the domestic cat has emerged as a prominent host of fleas that transmit the plague to veterinarians.

Diseases and Conditions Diseases Making a Comeback Slideshow

Diseases and Conditions Diseases Making a Comeback Slideshow

It's hard to believe, but the Black Death isn't just one for the history books or far-flung places. It's shown up recently in New Mexico, California, and Colorado, though it's still rare. Antibiotics can take care of it, but it can be life-threatening if it's not treated early enough. It's carried by rodents, like squirrels and mice, and the fleas that live on them.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.