The plague is a serious bacterial infection that can be deadly. Sometimes referred to as the “black plague,” the disease is caused by a bacterial strain called Yersinia pestis. This bacterium is found in animals throughout the world and is usually transmitted to humans through fleas.

The risk of plague is highest in areas that have poor sanitation, overcrowding, and a large population of rodents. Over the last 20 years, nearly all cases have been reported among people living in small and agricultural villages rather than overcrowded cities.

In medieval times, the plague was responsible for the deaths of millions of people in Europe.

Today, there are only 1,000 to 2,000 cases reported worldwide each year, with the highest incidence in Africa, particularly Madagascar.

The plague is a rapidly progressing disease that can lead to death if untreated. If you suspect you have it, call a doctor right away or go to an emergency room for immediate medical attention.

People who have the plague usually develop flu-like symptoms two to 6 days after infection. There are other symptoms that can help distinguish the three forms of the plague.

Bubonic plague symptoms

Symptoms of bubonic plague generally appear within two to 8 days of infection. They include:

  • fever and chills
  • headache
  • muscle pain
  • general weakness

You may also experience painful, swollen lymph glands, called buboes. These typically appear in the groin, armpits, neck, or site of the insect bite or scratch. The buboes are what give the bubonic plague its name.

Septicemic plague symptoms

Septicemic plague symptoms usually start within a few days after exposure, but septicemic plague can lead to death before symptoms even appear. Symptoms can include:

  • abdominal pain
  • diarrhea
  • nausea and vomiting
  • fever and chills
  • extreme weakness
  • bleeding (blood may not be able to clot)
  • shock
  • skin turning black (gangrene)

Pneumonic plague symptoms

Pneumonic plague symptoms may appear as quickly as one day after exposure to the bacteria. These symptoms include:

  • trouble breathing
  • chest pain
  • cough
  • fever
  • headache
  • overall weakness
  • bloody sputum (saliva and mucus or pus from the lungs)

There are three basic forms of plague:

Bubonic plague

The most common form of the plague is bubonic plague. It’s usually spread by the bite of an infected flea. In very rare cases, you can get the bacteria from material that has come into contact with a person who has the infection.

Bubonic plague infects your lymphatic system (a part of the immune system), causing inflammation in your lymph nodes. Untreated, it can move into the blood (causing septicemic plague) or to the lungs (causing pneumonic plague).

Septicemic plague

When the bacteria enter the bloodstream directly and multiply there, it’s known as septicemic plague. When they’re left untreated, both bubonic and pneumonic plague can lead to septicemic plague.

Pneumonic plague

When the bacteria spread to or first infect the lungs, it’s known as pneumonic plague — the most lethal form of the disease if untreated.

When someone with pneumonic plague coughs, the bacteria from their lungs are expelled into the air. Other people who breathe that air can also develop this highly contagious form of plague, which can lead to an epidemic.

While pneumonic plague can be fatal if left untreated, recovery rates are typically very high if treated within the first 24 hours when symptoms present themselves.

Pneumonic plague is the only form of the plague that can be transmitted from person to person.

People usually get the plague through the bite of fleas that have previously fed on infected animals like mice, rats, rabbits, squirrels, chipmunks, and prairie dogs. It can also be spread through direct contact with a person or animal that has the infection or by eating an infected animal.

Plague can also spread through scratches or bites of infected domestic dogs or cats.

Pneumonic plague can be spread from person to person through cough droplets that contain plague bacteria. It’s rare for bubonic plague or septicemic plague to spread from one human to another.

In most cases, being at risk of contracting the plague is relatively rare. However, there are a few factors that may increase your risk. These can include:

  • direct contact with someone who contracted the plague
  • homes with high exposure to rodents or fleas that may be infected with plague
  • living in a rural or semi-rural location that is extremely agricultural

Plague can be a life threatening disease if left untreated. If you have been exposed to rodents or fleas, have visited a region where plague is known to occur, and you develop symptoms of plague, contact your doctor immediately and have the following information available:

  • Be prepared to tell your doctor about any recent travel locations and dates.
  • Make a list of all over-the-counter medications, supplements, and prescription drugs you take.
  • Make a list of people who have had close contact with you.
  • Tell your doctor about all your symptoms and when they first appeared.

When you visit the doctor, emergency room, or anywhere else where others are present, wear a surgical mask to prevent the spread of the disease.

If your doctor suspects you may have the plague, they’ll check for the presence of the bacteria in your body:

  • A blood test can indicate whether you have septicemic plague.
  • To check for bubonic plague, your doctor will use a needle to take a sample of the fluid in your swollen lymph nodes.
  • To check for pneumonic plague, doctors will either take a blood sample or sample from the swollen lymph node and send it for laboratory testing.

The samples will be sent to a laboratory for analysis. Preliminary results may be ready in just 2 hours, but confirmatory testing takes 24 to 48 hours.

If the plague is suspected, your doctor will still begin treatment with antibiotics even before the diagnosis is confirmed. This is because the plague progresses rapidly, and being treated early can make a big difference in your recovery.

The plague is a life threatening condition that requires urgent care. If caught and treated early, it’s a treatable disease using antibiotics that are commonly available.

With no treatment, bubonic plague can multiply in the bloodstream (causing septicemic plague) or in the lungs (causing pneumonic plague). Death can occur within 24 hours after the appearance of the first symptom.

Treatment usually involves:

  • Strong and effective antibiotics such as gentamicin or ciprofloxacin, intravenous fluids, oxygen, and, sometimes, breathing support.
  • Those with pneumonic plague must be isolated from other patients in order to avoid transmission.
  • Treatment will continue for several weeks even after your fever breaks.
  • Those in contact with someone with plague will be closely monitored, and possibly given antibiotics as a preventative measure.

If diagnosed early, treatment for plague can be extremely successful with proper antibiotics. However, the main complication that may interfere with successful treatment is the timing of diagnosis and when treatment begins.

Plague can be fatal if not treated quickly, so it’s important to visit the doctor as soon as symptoms appear.

There are a few ways to prevent exposure to plague bacteria:

  • Keep the rodent population in your home and workplace under control.
  • Avoid keeping piles of debris such as firewood, rocks, and vegetation brush in areas you frequent.
  • Protect any outdoor pets from getting fleas by using flea control products.
  • If you are in high-risk areas of plague, dob’t allow pets to roam freely outside or sleep in your bed.
  • If your pet starts getting sick, visit the veterinarian right away.
  • Always wear insect repellent (chemical or natural) while outdoors.
  • Visit your doctor immediately if you believe you’ve been exposed to infected rodents or fleas.
  • Be able to recognize symptoms of each type of plague in order to get treated as soon as possible.
  • Avoid direct contact with those you suspect have been exposed to plague bacteria.

There’s currently no commercially available vaccine against plague in the United States. So it’s important to take preventive measures in avoiding any contact with plague or any creature that carries it.

Epidemics of plague killed millions of people (about one-quarter of the population) in Europe during the Middle Ages. It came to be known as the “black death.” That’s not quite the case anymore.

Today the risk of developing plague is quite low, with only 3,248 cases and 584 deaths reported to the World Health Organization (WHO) from 2010 to 2015.

Outbreaks are generally associated with infected rats and fleas in the home. Crowded living conditions and poor sanitation also increase the risk of plague.

Today, most human cases of the plague occur in Africa, though they do appear elsewhere. The countries in which the plague is most common are Madagascar, the Democratic Republic of Congo, and Peru.

The plague is rare in the United States, but the disease is still sometimes found in the rural Southwest, in particular Arizona, Colorado, and New Mexico. The last epidemic of plague in the United States occurred in 1924 to 1925 in Los Angeles.

In the United States, reported cases average seven per year. Most have been in the form of the bubonic plague. There hasn’t been a case of person-to-person transmission of the plague in U.S. urban areas since 1924.

In 2019, the Center for Disease Control and Prevention (CDC) reported only one case of the plague in the United States.

Plague can lead to gangrene if blood vessels in your fingers and toes disrupt blood flow and cause death to tissue. In rare cases, plague can cause meningitis, an inflammation of membranes that surround your spinal cord and brain.

Getting treatment as quickly as possible is crucial to stop the plague from becoming deadly.