What to know about plague

What to know about plague

Plague is a deadly viral disease that affects mammals, including humans. It can spread through animal or human contact.

Many areas of the world, including the United States, are home to the bacteria that cause the plague. The plague can be deadly without treatment.

The history of the plague as well as symptoms, causes, and treatment will be discussed in this article.

What is plague?

What is plague?

Plague is a sickness caused by the bacterium Yersinia pestis (Y. pestis). Plague bacteria are normally present in small mammals, such as rats, and in fleas that live on them. Infected fleas can transfer plague bacteria on to different mammals that they feed on, including humans.

There are three types of plague:

  • Bubonic plague: The transmission of bubonic plague often happens through flea bites. Bubonic plague bacteria attack lymph nodes, which are small glands that help the body fight infection. The plague bacteria cause the lymph nodes to become tender and swollen. These infected lymph nodes are called buboes.
  • Pneumonic plague: Pneumonic plague is the most harmful form of plague. It affects the lungs and can develop in as little as 24 hours. If not treated quickly, it can be fatal. Pneumonic plague is also the only form of plague that can spread through human contact.
  • Septicemic plague: Septicemic plague symptoms can occur as the first signs of plague, or they can be a result of untreated bubonic plague. A person with septicemic plague may develop black, dying skin tissue.

Origins and history

For thousands of years, plague bacteria have been around. The presence of plague bacteria in their DNA was found in studies performed on two Bronze Age skeletons. The skeletons were about 3,800 years of age.

Historically, the plague bacterium Y. Pestis was responsible for the Justinian plague, the Black Death, and the Southwest China pandemic that broke out in the 19th century.

The Justinian plague

The Justinian plague struck Turkey in the sixth century and extended between 541 C.E. to Asia , Africa, Europe , and the Middle East. 750 C.E. and In just 4 years, between 542 C.E. The Justinian plague, in 546 C.E., killed about 100 million people in Asia, Africa , and Europe.

Death of the Black

In the 14th century, the most infamous plague, the Black Death, took place in Europe. At least a third of the population of Europe died between 1347 and 1352 from the plague, which is approximately 25 million people.

Over the next 400 years, plague outbreaks have resurfaced across Europe. In 1656–1657, two thirds of the population of Naples and Genoa died from the plague. London and Vienna each lost around 100,000 people to the plague between 1665 and 1666. In 1770-1771, Moscow had over 100,000 people who died of the plague.

In total, over 50 million deaths in Europe were caused by the Black Death.

Outbreak in China

There was a plague outbreak in the province of Yunnan in southwest China around 1855. In 1910-1920, the plague eventually spread through trade ships to India, Australia , Japan, and North and South America. By 1959, over 15 million individuals were killed by the plague outbreak.


In the human body, the three forms of plague have differing symptoms. All forms of plague can, however, cause:

  • sudden fever
  • weakness
  • nausea
  • vomiting
  • diarrhea
  • abdominal pain
  • headache
  • body aches

Bubonic plague

A person with bubonic plague will generally notice symptoms within 2 to 6 days after exposure to the plague bacteria, according to the Centers for Disease Control and Prevention ( CDC).

Bubonic plague symptoms include:

  • one or more swollen, tender lymph nodes
  • muscle pain
  • feeling of discomfort

The buboes formed by bubonic plague are firm and painful and will often appear near the groin, armpit, or neck. If left untreated, these buboes can form into open, pus-filled sores.

Pneumonic or septicemic plague may also develop into untreated bubonic plague.

Pneumonic plague

After exposure to the bacteria, pneumonic plague may develop as fast as 1 day.

Pneumonic plague symptoms include:

  • rapid heartbeat
  • difficulty breathing
  • pneumonia
  • cough
  • chest pain
  • shortness of breath
  • bloody or watery mucus

A pneumonic plague can quickly lead to organ failure, shock, or death if left untreated. Recovery rates for pneumonic plague, however, are high if a person receives treatment within 24 hours of developing symptoms.

Septicemic plague
Septicemic plague can develop from bubonic plague. It can occur independently of other plagues as well.

Symptoms of septicemic plague can include:

  • Fatigue
  • muscle pain
  • bleeding into skin or other organs
  • black, dying tissue, particularly on fingers , toes, and nose

Septicemic plague progresses quickly and, if left untreated, can be fatal.

A person with any symptoms of the plague should seek immediate medical attention.


A bite from an infected flea is the most common cause of plague in humans. There is also a risk that people who come into direct contact with infected fluids or tissues from animals with plague may be affected.

When inhaling droplets breathed out by a person, dog, or cat who has pneumonic plague, plague can also spread to people. The only type that can spread from person to person is the pneumonic plague.

Treatment and prevention

By collecting a person’s blood, sputum, or lymph node tissue sample, doctors can diagnose a plague. It can take up to 2 days to confirm the plague in the laboratory, so a doctor may start treating a person with suspected plague after taking their samples.

With antibiotics, doctors can treat the plague. It may be necessary to place them in an isolation room in the hospital if a person has pneumonic plague.

Although, according to the CDC, the plague can start at any time of year, most cases in the U.S. occur from late spring to early fall. Additionally, in rural areas, such as New Mexico, Arizona, and Colorado, plague is most common.

People living in plague-threatened areas should take care to avoid rodents and fleas, such as rats, squirrels, or chipmunks. In these areas , people should also avoid handling animal carcasses.

Today, is there a plague?

The CDC reports that an average of seven plague cases occur each year in the U.S. In the United States, over 80 percent of plague cases have been bubonic plague. People aged 12-45 make up 50 per cent of U.S. cases of plague, although people of any age can be affected by plague.

The majority of human cases of plague between the 1990s and 2018 occurred in Africa, according to the CDC. The CDC also states that, rather than in larger cities, most cases of plague have been found in small towns or villages.

The World Health Organization (WHO) found that the Democratic Republic of Congo, Madagascar, and Peru were the countries with the most prevalent levels of plague in the world in 2017.

Similar illnesses

There are several diseases that have similar symptoms to plague. They include:

  • tularemia, a rare infectious disease passed on from small mammals to humans via infected ticks or flies
  • cat scratch disease, also known as cat scratch fever, which a person can get through a bite, lick, or scratch from an infected cat
  • Rocky Mountain spotted fever, a bacterial infection spread through a bite of an infected tick
  • elephantiasis, a disease where parasitic worms infect the lymph system
  • brucellosis, an infection that can occur after a person has consumed unpasteurized cheese or milk
  • dengue virus disease, a viral infection spread by mosquitoes
  • streptococcal lymphadenitis, an infection of the lymph nodes


While plague is less common than it once was, there are still parts of the world where it can be obtained by a person. People living in rural U.S. areas should make sure that contact with rodents, fleas, and carcasses of animals is avoided.

Typically, plague is easy to treat with antibiotics. However, when left untreated, it can be fatal.

An individual who notices any signs of the plague should immediately seek medical attention.