Plague is a serious bacterial infection that's transmitted primarily by fleas. The organism that causes plague, Yersinia pestis, lives in small rodents found most commonly in rural and semirural areas of Africa, Asia and the United States. The organism is transmitted to humans who are bitten by fleas that have fed on infected rodents or by humans handling infected animals.
Known as the Black Death during medieval times, today plague occurs in fewer than 5,000 people a year worldwide. It can be deadly if not treated promptly with antibiotics. The most common form of plague results in swollen and tender lymph nodes — called buboes — in the groin, armpits or neck. The rarest and deadliest form of plague affects the lungs, and it can be spread from person to person.
Plague is divided into three main types — bubonic, septicemic and pneumonic — depending on which part of your body is involved. Signs and symptoms vary depending on the type of plague.
Bubonic plague is the most common variety of the disease. It's named after the swollen lymph nodes (buboes) that typically develop in the first week after you become infected. Buboes may be:
- Situated in the groin, armpit or neck
- About the size of a chicken egg
- Tender and firm to the touch
Other bubonic plague signs and symptoms may include:
- Sudden onset of fever and chills
- Fatigue or malaise
- Muscle aches
Septicemic plague occurs when plague bacteria multiply in your bloodstream. Signs and symptoms include:
- Fever and chills
- Extreme weakness
- Abdominal pain, diarrhea and vomiting
- Bleeding from your mouth, nose or rectum, or under your skin
- Blackening and death of tissue (gangrene) in your extremities, most commonly your fingers, toes and nose
Pneumonic plague affects the lungs. It's the least common variety of plague but the most dangerous, because it can be spread from person to person via cough droplets. Signs and symptoms can begin within a few hours after infection, and may include:
- Cough, with bloody mucus (sputum)
- Difficulty breathing
- Nausea and vomiting
- High fever
- Chest pain
Pneumonic plague progresses rapidly and may cause respiratory failure and shock within two days of infection. Pneumonic plague needs to be treated with antibiotics within a day after signs and symptoms first appear, or the infection is likely to be fatal.
When to see a doctor
If you begin to feel ill and have been in an area where plague has been known to occur, seek immediate medical attention. You'll need treatment with medication to prevent serious complications or death.
In the United States, plague has been transmitted to humans in several western and southwestern states — primarily New Mexico, Arizona, California and Colorado. Worldwide, plague is most common in rural and semirural parts of Africa (especially the African island of Madagascar), South America and Asia.
The plague bacteria, Yersinia pestis, is transmitted to humans through the bites of fleas that have previously fed on infected animals, such as:
- Prairie dogs
The bacteria can also enter your body if a break in your skin comes into contact with an infected animal's blood. Domestic cats and dogs can become infected with plague from flea bites or from eating infected rodents.
Pneumonic plague, which affects the lungs, is spread by inhaling infectious droplets coughed into the air by a sick animal or person.
The risk of developing plague is very low. Worldwide, only a few thousand people develop plague each year. However, your plague risk can be increased depending on the area where you live and travel, your job, and your hobbies.
Plague outbreaks are most common in rural and semirural areas that are overcrowded, have poor sanitation and have a high rodent population. The greatest number of human plague infections occur in Africa, especially the African island of Madagascar. Plague has also been transmitted to humans in parts of Asia and South America.
In the United States, plague is rare, but it has been known to occur in several western and southwestern states — primarily New Mexico, Arizona, California and Colorado.
Veterinarians and their assistants have a higher risk of coming into contact with domestic cats and dogs that may have become infected with plague. People who work outdoors in areas where plague-infected animals are common are also at higher risk of getting plague.
Camping, hunting or hiking in areas where plague-infected animals reside can increase your risk of being bitten by an infected flea.
Complications of plague may include:
- Death. Most people who receive prompt antibiotic treatment survive bubonic plague. Untreated plague has a high fatality rate.
- Gangrene. Blood clots in the tiny blood vessels of your fingers and toes can disrupt blood flow and cause that tissue to die. The portions of your fingers and toes that have died may need to be removed (amputated).
- Meningitis. Rarely, plague may cause inflammation of the membranes surrounding your brain and spinal cord (meningitis).
No effective vaccine is available, but scientists are working to develop one. Antibiotics can help prevent infection if you're at risk of or have been exposed to plague. Take the following precautions if you live or spend time in areas where plague outbreaks occur:
- Rodent-proof your home. Remove potential nesting areas, such as piles of brush, rock, firewood and junk. Don't leave pet food in areas that rodents can easily access. If you become aware of a rodent infestation, take steps to control it.
- Keep your pets free of fleas. Ask your veterinarian which flea-control products will work best.
- Wear gloves. When handling potentially infected animals, wear gloves to prevent contact between your skin and harmful bacteria.
- Use insect repellent. Closely supervise your children and pets when spending time outside in areas with large rodent populations. Use insect repellent.