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

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
• Headache
• Fatigue or malaise
• Muscle aches

Septicemic plague

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
• Shock
• Blackening and death of tissue (gangrene) in your extremities, most commonly your fingers, toes and nose

Pneumonic plague

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
• Headache
• Weakness
• 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:

• Rats
• Mice
• Squirrels
• Rabbits
• Prairie dogs
• Chipmunks
• Voles

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.

Location

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.

Job

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.

Hobbies

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.

If your doctor suspects plague, he or she may look for the Yersinia pestis bacteria in samples taken from your:

• Buboes. If you have the swollen lymph nodes (buboes) typical of bubonic plague, your doctor may use a needle to take a fluid sample from them (aspiration).
• Blood. You'll generally have Yersinia pestis bacteria present in your bloodstream only if you have septicemic plague.
• Lungs. To check for pneumonic plague, your doctor will take mucus (sputum) or fluid from your airways using a thin, flexible tube inserted through your nose or mouth and down your throat (endoscopy).

Medications

As soon as your doctor suspects that you have plague, you'll need to be admitted to a hospital. You'll receive powerful antibiotics, such as:

• Gentamicin
• Doxycycline (Monodox, Vibramycin, others)
• Ciprofloxacin (Cipro)
• Levofloxacin
• Moxifloxacin (Avelox)
• Chloramphenicol

If you suspect you have plague, you're likely to start by going to an emergency room. You may eventually need to see a doctor specializing in infectious disease.

What you can do

If you have respiratory symptoms, you may need to wear a surgical mask to your appointment to help prevent spreading the disease to others. You might also want to:

• Tell your doctor about any relevant travel or possible plague exposures you've had.
• Write down any symptoms you're experiencing, including when they started.
• Write down key personal information, including whether you've recently traveled to an area where plague is common and whether you've handled wild animals.
• Make a list of all medications, vitamins or supplements you're taking.
• Bring a family member or friend along, if possible. Sometimes it can be difficult to retain all the information you get during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

For plague, some basic questions to ask your doctor include:

• What is likely causing my symptoms or condition?
• Other than the most likely cause, what are other possible causes for my symptoms or condition?
• What tests do I need?
• What is the best course of action?
• Will I need to be in isolation?
• What are the alternatives to the primary approach you're suggesting?
• I have other health conditions. How can I best manage them together?
• Are there any restrictions I need to follow?

Don't hesitate to ask any other questions.

What to expect from your doctor

Your doctor is likely to ask you a number of questions, including:

• When did you begin experiencing symptoms?
• Have you recently traveled to areas where plague is common?
• Have you recently handled wild animals or cats?
• Are you aware of having been bitten by fleas?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?