Plague: Bubonic, Pneumonic, and Septicemic

Medically Reviewed by Zilpah Sheikh, MD on November 13, 2023
6 min read

Plague is an infectious disease that affects people and animals. Once called the Black Death, this disease that swept the world hundreds of years ago still lives. And it’s still dangerous.

It's caused by bacteria called Yersinia pestis. It’s usually spread by fleas. These bugs pick up the germs when they bite infected animals like rats, mice, or squirrels. Then they pass it to the next animal or person they bite. You can also catch the plague directly from infected animals or people.

Fortunately, we know more than our ancestors did about how to handle infectious diseases. These days, with quick treatment, the plague can be cured.

Plague spreads easily among people, usually by droplets in the air that come out when infected people sneeze or cough. This can lead to epidemics. 

Thanks to treatment and prevention, the plague is rare now. Only a few thousand people around the world get it each year. Most of the cases are in Africa (especially the Democratic Republic of Congo and Madagascar), India, and Peru.

The U.S. sees about seven cases a year, mostly in rural or remote areas in Southwestern states like Arizona, Colorado, New Mexico, and California.

Scientists have found DNA signs of the plague in Bronze Age skeletons that are nearly 3,800 years old. The first plague pandemic, called the Justinian plague, struck in the years 541 and 542. Many waves of plague swept Europe and Asia from the 6th to 8th centuries.

The second pandemic, the one known as the Black Death, arrived in Italy in 1347. Historians believe it started in Central Asia and came to Europe aboard trading ships, carried by fleas and rats. It spread quickly across Europe, and in the next 5 years, about a third of the continent's population died. 

This second pandemic ended around 1400, but Europe still had deadly outbreaks in the next 400 years. In the mid-1600s, plague in Italy killed two-thirds of the population of Naples and Genoa, and London lost roughly a quarter of its population. An outbreak in Moscow in 1770 killed about 100,000 people. 

The third plague pandemic started in southwest China in 1855. It spread from there, killing about 70,000 people in Canton. It reached Japan, Australia, and North and South America in the early 1900s. Experts estimate plague killed 12 million people in India in the late 1800s and early 1900s. 

There are three main types of plague

Bubonic plague

This is usually caused by a flea bite. Within 2 to 8 days, your lymph nodes begin to swell as the bacteria builds up. These swollen glands are called "buboes."

Septicemic plague

It can be caused by a flea bite or by touching an animal that has plague. It can also develop from bubonic plague if it's not treated and the bacteria infects your blood. It's not clear how long it'll take you to start feeling sick, but it'll probably happen within days.

Pneumonic plague

This is the most serious type, and it's the only one that can spread from person to person. You can get it from breathing in droplets that come out when an infected person sneezes or coughs. It also can happen when you have bubonic or septicemic plague and the bacteria spreads to your lungs. It takes only 1 to 3 days to become sick.

After people catch the plague, the symptoms start 1-8 days later. You feel very sick and weak and may have a fever, chills, and headaches. Other symptoms depend on which of the three kinds of plague you have:

Symptoms of bubonic plague

This is the most common type. Aside from a fever, headache, and chills, the main symptom is buboes. Those swollen and painful lymph nodes can be under your arms, in your neck, or in your groin. Without treatment, the bacteria can spread to other parts of your body.

Symptoms of septicemic plague

This type is more dangerous than bubonic plague. Signs include:

  • Bleeding under your skin or from your mouth, nose, or bottom
  • Blackened skin, especially on your nose, fingers, and toes
  • Belly pain, diarrhea, vomiting, and shock

Symptoms of pneumonic plague

This is the rarest form of the disease. It’s deadly without treatment. Symptoms include:

The bacteria that causes plague may live in certain animals without causing them to die. Scientists think that creates what they call a "long-term reservoir," or supply, of the bacteria. Plague outbreaks can happen anywhere people come in contact with those reservoirs of bacteria.

Some living conditions can make outbreaks of plague more likely. Cities that are overcrowded, lack systems for removing trash and human waste, and have large amounts of rats can be breeding grounds for plague.

For most people, the chances of getting the plague are low. But it's more likely if you visit or live in an area with the plague and you:

  • Touch a living or dead animal that might have been infected, like a rat, mouse, squirrel, rabbit, or chipmunk
  • Work with animalsregularly
  • Spend a lot of time outdoors working, hiking, camping, or hunting
  • Spend time with someone who has the plague

Your doctor might suspect you've been infected with plague if you have certain symptoms and live in an area where animals are known to carry it or have visited such a place recently. 

To find out if you have plague, your doctor will take samples from your body. Those could include blood or tissue from a swollen lymph gland. The samples are sent to a lab, which tests them for the bacteria that causes plague.

In the past few years, researchers have come up with a rapid test that can spot signs of the plague bacteria within 15 minutes. It tests fluid from infected lymph nodes or that you cough up. It's not widely used, but it could be an important first test in parts of the world where it isn't as easy to get samples tested in a lab. 

If you’ve been in an area with the plague and have symptoms, get to a doctor right away. Hours can make a difference. 

If you’ve been around someone who has the plague, your doctor may start treatment even if you don’t have symptoms. If you must be near the person, wear tight-fitting disposable surgical masks so you won’t breathe in the plague bacteria.

If you have the plague, you'll be admitted to the hospital. You'll get antibiotics like:

  • Ciprofloxacin (Cipro)
  • Doxycycline (Vibramycin)
  • Gentamicin (Garamycin)
  • Levofloxacin (Levaquin)

Treatment works well. With antibiotics, most people get better within a week or two. But without treatment, most people with the plague die.

There’s no vaccine for the plague in the U.S. So if you have a chance of contact with plague germs, take steps to protect yourself.

If you travel to Africa, Asia, or South America, check for traveler notices about plague outbreaks on the CDC website. Avoid areas with the plague if you can, and stay away from sick or dead animals while you’re there.

If you live in an area where there’s been a case of the plague:

  • Fill holes and gaps in your home to stop mice, rats, and squirrels from getting in.
  • Clean up your yard. Get rid of piles of leaves, wood, and rocks where animals might make their homes.
  • Use bug repellent with DEET to prevent flea bites when you hike or camp.
  • Wear gloves if you have to touch wild animals, alive or dead.
  • Use flea control sprays or other treatments on your pets.
  • Don’t let outdoor pets like cats or dogs sleep in your bed.