What Is Bubonic Plague? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Widely known as the “Black Death,” the disease that killed 50 million people in Europe’s Middle Ages, bubonic plague is still with us — although cases are relatively rare.

Bubonic plague is one of three life-threatening diseases caused by Yersinia pestis (Y. pestis), a bacteria found in small animals and their fleas. If left untreated, bubonic plague can be fatal; however, it can be easily treated with antibiotics. (1)

Bubonic plague is usually caused by the bite of an infected flea. When Y. pestis bacteria enter the body, it infects the nearest lymph node, causing it to become swollen, tender, and painful.

The bacteria can then travel through the lymphatic system and result in swollen lymph nodes, or buboes, from which bubonic plague gets its name. These will usually develop in and around the groin, armpits, and neck.

Other symptoms, which tend to develop within three to seven days of the initial infection, include the following:

• Fever
• Chills
• Weakness
• Aches
• Nausea
• Vomiting

Bubonic plague is caused by Y. pestis, a bacteria transmitted to humans through fleas that have been infected by animals such as rats, mice, squirrels, rabbits, chipmunks, and prairie dogs. Rodents are the main carriers of the bacteria.

Y. pestis can also enter your body if your skin is broken and you come into contact with an infected animal’s blood. The risk of contracting bubonic plague is very low, but it can increase depending on where you live, what you do for a living, and your recreational pastimes.

Rural areas that have a high number of rodents, for example, are at a higher risk for bubonic plague. Cases in the United States are rare but tend to occur in Western and Southwestern states. If you work outdoors or with animals, this could also put you at an increased risk, as can hunting and camping where plague-infected critters live. (2)

To diagnose bubonic plague, your doctor will send a sample of your blood or lymph nodes to a lab for testing. According to the Centers for Disease Control and Prevention (CDC), preliminary results may be available in two hours, and official confirmation takes 24 to 48 hours. (3)

The duration of cases vary. After administration of antibiotics, symptoms usually take two to five days to resolve. (4)

Buboes may remain for several weeks after treatment, possibly longer if you have a severe case or develop septicemic or pneumonic plague. (5)

Prognosis of Bubonic Plague

If untreated, the prognosis is poor, with mortality rates estimated at 50 to 90 percent. (6)

In the United States, the overall mortality rate is 11 percent. (3)

Bubonic plague can rapidly get worse and become life-threatening, so your doctor will begin treatment immediately after your diagnosis. The condition requires hospitalization, and if you contract pneumonic plague, you will be isolated in a private room to prevent person-to-person spread.

Medication Options

Bubonic plague can usually be successfully treated with various antibiotics:

• gentamicin (Garamycin)
• streptomycin
• levofloxacin (Levaquin)
• ciprofloxacin (Cipro)
• doxycycline (Vibramycin)
• moxifloxacin (Avelox)

Prevention of Bubonic Plague

Unfortunately, there is no vaccine available to protect you from bubonic plague. If you think you’ve been exposed to it, antibiotics can be taken to prevent infection.

You won’t have to be quarantined, but care will need to be taken to ensure that the infection doesn’t spread from you to others through tissue, blood, or other fluids. (3)

In addition, you may want to take the following precautions: (7)

• Rodent-proof your home. Get rid of areas where rodents may nest, such as piles of brush and firewood. Avoid leaving food where rodents can access it.
• Wear gloves. If you must handle a potentially infected animal, wear gloves to prevent contact between your skin and the bacteria.
• Use insect repellent. DEET-containing products can protect you from rodent fleas when you’re hiking, camping, or working outdoors.
• Keep pets flea-free. Apply flea-control products to your pets regularly.

Left untreated, bubonic plague can spread from the lymphatic system to the bloodstream or the lungs, causing septicemic (blood) or pneumonic (lung) plague.

Septicemic plague occurs when the bacteria multiply in your bloodstream. In addition to the symptoms of bubonic plague, septicemic plague can cause the following:

• Abdominal pain
• Septic shock (a life-threatening condition in which the vital organs of the body stop working due to infection spreading throughout the body)
• Diarrhea and vomiting
• Bleeding
• Gangrene (death of body tissue due to lack of blood flow), usually in extremities such as your nose, fingers, and toes

Pneumonic plague is the least common type of plague, but it’s the most dangerous because it can be spread via cough droplets from person to person. Pneumonic plague causes the following symptoms:

• Cough
• Shortness of breath
• Chest pain
• Bloody sputum (a mixture of saliva and mucus produced when you cough)
• High fever
• Extreme weakness

As it progresses, pneumonia from plague can cause respiratory failure and shock. If not treated by antibiotics within 24 hours of symptoms, it can be fatal.

In the United States, cases of bubonic plague are rare. The CDC reports that in recent decades, in humans, there’s been an average of seven cases of plague a year. (3) Most U.S. cases occur in northern New Mexico, northern Arizona, southern Colorado, southern Oregon, and California. (8)

Bubonic plague can affect people of any age, but 50 percent of reported cases occur in people between 12 and 45 years old. It occurs in both men and women but is slightly more common in men. (8)

A study looked at the history of plague in the United States and examined how the disease has affected different populations, including Black, Indigenous, and People of Color (BIPOC) communities. According to the study, among the 1,006 cases of human plague reported between 1900 and 2012, American Indians and Asian Americans each accounted for 16 percent of cases, and those who identified as Hispanic accounted for 12 percent. Black individuals represented only 1 percent of cases. White individuals accounted for 55 percent of cases, and race or ethnicity were unknown in 20 percent of cases.

Between 1965 and 2012, people who identified as American Indians represented a much larger number of cases — 33 percent — compared with previous years. (9)

In rare cases, bubonic plague may cause meningitis, a condition in which the membranes surrounding your brain and spinal cord become infected and start to swell. Symptoms include a headache, fever, and stiff neck. Immediate treatment with antibiotics can prevent serious complications.

The CDC has detailed and up-to-date information on this and other rare diseases.

With additional reporting by Carlene Bauer.