Plague
Bubonic plague; Pneumonic plague; Septicemic plague
Plague is a severe bacterial infection that may cause death.
Different types of fleas prefer specific animals as hosts, but will infest humans if their specific hosts are unavailable. Fleas can carry plague and typhus. They are also thought to transmit several other diseases. (Image courtesy of the Centers for Disease Control and Prevention.)
Fleas are blood-feeding insects. Pain and itching results from an allergic reaction to the materials that the fleas inject into the skin at the time of the bite.
Antigens are large molecules (usually proteins) on the surface of cells, viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, drugs, and foreign particles. The immune system recognizes antigens and produces antibodies that destroy substances containing antigens.
Causes
Plague is caused by the bacteria Yersinia pestis. Rodents, such as rats, carry the disease. It is spread by fleas.
People can get plague when they are bitten by a flea that carries the plague bacteria from an infected rodent. In rare cases, people get the disease when handling an infected animal.
Plague lung infection is called pneumonic plague. It can be spread from person to person. 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 can be started this way.
In the Middle Ages in Europe, massive plague epidemics killed millions of people. Plague has not been eliminated. It can still be found in Africa, Asia, and South America.
Today, plague is rare in the United States. But it has been known to occur in parts of California, Arizona, Colorado, and New Mexico.
There three most common forms of plague are:
- Bubonic plague, an infection of the lymph nodes
- Pneumonic plague, an infection of the lungs
- Septicemic plague, an infection of the blood
The time between being infected and developing symptoms is typically 2 to 8 days. But the time can be as short as 1 day for pneumonic plague.
Risk factors for plague include a recent flea bite and exposure to rodents, especially rabbits, squirrels, or prairie dogs, or scratches or bites from infected domestic cats.
Symptoms
Bubonic plague symptoms appear suddenly, usually 2 to 5 days after exposure to the bacteria. Symptoms include:
- Fever and chills
- General ill feeling (malaise)
- Headache
- Muscle pain
- Seizures
- Smooth, painful lymph gland swelling called a bubo that is commonly found in the groin, but may occur in the armpits or neck, most often at the site of the infection (bite or scratch); pain may start before the swelling appears
Pneumonic plague symptoms appear suddenly, typically 1 to 4 days after exposure. They include:
- Severe cough
- Difficulty breathing and pain in the chest when breathing deeply
- Fever and chills
- Headache
- Frothy, bloody sputum
Septicemic plague may cause death even before severe symptoms occur. Symptoms can include:
- Abdominal pain
- Bleeding due to blood clotting problems
- Diarrhea
- Fever
- Nausea, vomiting
Exams and Tests
The health care provider will perform a physical examination and ask about your symptoms.
Tests that may be done include:
- Blood culture
- Culture of lymph node aspirate (fluid taken from an affected lymph node or bubo)
- Sputum culture
- Chest x-ray
Treatment
People with the plague need to be treated right away. If treatment is not received within 24 hours of when the first symptoms occur, the risk for death increases.
Antibiotics such as streptomycin, gentamicin, doxycycline, or ciprofloxacin are used to treat plague. Oxygen, intravenous fluids, and respiratory support are usually also needed.
People with pneumonic plague must be kept away from other patients and isolation procedures will be followed in the hospital. People who have had contact with anyone infected by pneumonic plague should be watched carefully and given antibiotics as a preventive measure.
Outlook (Prognosis)
Without treatment, about 50% of people with bubonic plague die. Almost everyone with septicemic or pneumonic plague dies if not treated right away. Treatment reduces the death rate to 50%.
When to Contact a Medical Professional
Contact your provider if you develop plague symptoms after exposure to fleas or rodents. Contact your provider if you live in or have visited an area where plague occurs.
Prevention
Rat control and watching for the disease in the wild rodent population are the main measures used to control the risk for epidemics. The plague vaccine is no longer used in the United States.
References
Mead PS, Nelson CA. Plague and other Yersinia infections. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 296.
Mead PS. Plague (Yersinia pestis). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 229.
Version Info
Last reviewed on: 6/20/2021
Reviewed by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
