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and Carola Felchner, science journalist

Fabian Dupont is a freelance writer in the medical department. The human medicine specialist is already doing scientific work in Belgium, Spain, Rwanda, the USA, Great Britain, South Africa, New Zealand and Switzerland, among others. The focus of his doctoral thesis was tropical neurology, but his special interest is international public health and the comprehensible communication of medical facts.

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Carola Felchner is a freelance writer in the medical department and a certified training and nutrition advisor. She worked for various specialist magazines and online portals before becoming a freelance journalist in 2015. Before starting her internship, she studied translation and interpreting in Kempten and Munich.

More about the experts All content is checked by medical journalists.

The plague is a serious infectious disease that can be fatal. The trigger is the bacterium Yersinia pestis, which is transmitted to humans by rat fleas. The plague no longer plays a role in Europe today, but it does play a role in some regions of Africa, Asia and South, Central and North America. Read how you can protect yourself from infection in such risk areas and how the plague is treated!

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. A20

Brief overview

What is plague Highly contagious infectious disease transmitted by rodent fleas. No longer plays a role in Europe today.
Symptoms: Depending on the form, e.g. B. high fever, chills, swollen lymph nodes, black / bluish skin coloration, bloody sputum
Cause: The trigger is the bacterium Yersinia pestis, which is transmitted through flea bites and can also be passed on from person to person. The infection rarely occurs through direct contact with infected rodents. In pneumonic plague, droplet infection is the most important transmission route. Risk factors include: poor hygiene standards.
Treatment: antibiotics
Prognosis: good if therapy is started early, otherwise the disease is usually fatal.

Plague: description

Fortunately, the times when the plague ("Black Death") wiped out entire villages are over. Today the infectious disease no longer plays a role in Europe. It is caused by the bacterium Yersinia pestis. Rodents such as rats and mice are the reservoir of the pathogen. The bacterium can be transmitted from animals to humans via fleas. It is rare for humans to be directly infected by sick rodents. Diseases that can be transmitted from vertebrates (such as rats) to humans (and vice versa) like the plague are known as zoonoses.

People infected with the plague can pass the pathogen on to other people. This happens especially with pneumonic plague. It is transmitted via droplet infection.

A vaccine against plague is not available in Germany.

Plague: Contained, but not eradicated

The risk of contracting plague is particularly high in areas where there are pest-infected wild rodents. According to the Robert Koch Institute, however, this is only the case in limited endemic areas in Africa, Asia, tropical Central and South America and the southwest of the USA. The spread of the plague is favored when many people live together in a confined space under poor hygienic conditions.

Major epidemics and pandemics, which claimed millions of victims in the Middle Ages, no longer exist today.

Between 2010 and 2015, the World Health Organization (WHO) registered 3,248 plague cases worldwide, including 584 deaths. This number is very imprecise, however, as more than 80 percent of infections occur in Africa, where not all cases are reported to the WHO. Incidentally, in Germany, too, there is an obligation to report in accordance with the Infection Protection Act (IfSG) for any suspicion of plague, proven illnesses and deaths from plague.

Along with cholera, smallpox and yellow fever, the plague is one of the four quarantine diseases as defined by the World Health Organization (WHO). These diseases have a particularly threatening disease course and are extremely contagious.

Plague: symptoms

The period of time between infection with the plague pathogen and the appearance of the first symptoms (incubation period) varies considerably. It ranges from a few hours to up to seven days.

Basically there are three different main forms of the plague in humans, some with different plague symptoms.

bubonic plague

The bubonic plague, also known as bubonic plague or black death, is the most common and well-known form of the plague. It is generally only transmitted through flea bites. The first symptoms usually appear two to six days after infection:

high fever
chills
headache
general feeling of weakness

Small blisters sometimes form at the point where the plague bacteria penetrated the skin through a flea bite. Sometimes a mild, red rash will develop in later stages. The plague pathogens migrate to the neighboring lymph nodes, which swell due to the infection and can easily be felt. The swollen regions are hard and painful with the bubonic plague. The groin, armpit and neck, where the major lymph node stations are located, are often affected. In the further course of the disease, the disease spreads and lymph nodes further away also swell.

As with a bruise, the lymph node swellings turn blue within a few days, creating the typical appearance of dark bumps in plague sufferers. They rarely open and empty highly infectious secretions.

This is how bubonic plague is transmitted

Rodent fleas that carry the pathogen get on human skin. After the flea bite, the pathogens spread through the lymphatic system.

If the lymph nodes bleed in, complications can arise. Because then there is a risk of bacteria getting into the blood or lungs. Then a so-called plague sepsis or pulmonary plague can result. Both forms of the disease are serious and often fatal.

Pulmonary plague

Pulmonary plague occurs either as a complication of the bubonic plague or as an "independent" illness after the plague pathogen is transmitted via droplet infection: Sick people distribute tiny droplets of secretion into the surrounding air when they speak, cough or sneeze. These droplets contain plague bacteria and are highly contagious. When healthy people breathe them in, the bacteria go straight to the lungs and cause pneumonic plague.

The first symptoms of pneumonic plague develop a few hours after the plague pathogen has reached the lungs. At first, the patient only has a fever, may have chills and / or headaches, and generally feels weak. On the second day, coughing, often with (bloody) sputum, and chest pain are added. The patient has a rapid pulse and shortness of breath. Because of the strong coughing stimulus, those affected often vomit or have abdominal pain.

Plague sepsis

In about ten percent of all cases, the plague bacteria get into the blood and cause "blood poisoning". This so-called plague sepsis occurs as a complication of bubonic or pulmonary plague. Symptoms include dropping blood pressure, a high fever, confusion or lethargy, and digestive problems.

Since the pathogens can spread throughout the body via the blood, the consequences of plague sepsis are diverse and can affect different organs. Coagulation disorders are particularly dangerous because they are associated with bleeding inside the body. Heart stumbling, enlarged spleen and liver, and kidney failure are other possible consequences.

If left untreated, the plague sepsis leads to circulatory failure. If blood flow cannot be maintained in the body, the patient dies of plague sepsis.

Plague: causes and risk factors

The fact that the plague could rage so extremely in earlier times was due to the fact that people did not know its cause and therefore could not prevent infection. It has only been known for a good 120 years that the plague is caused by a bacterium (Yersinia pestis). The pathogen is mainly found in rodents and can be transmitted to humans by their fleas. Sick people can also pass the plague bacteria directly on to other people. In the case of pneumonic plague, this happens via droplet infection.

The plague bacterium is highly contagious. It can also trick people's immune system with a special mechanism: Certain white blood cells are important defense cells of the immune system. They can "eat up" invaders such as bacteria and thus stop an infection. Not so with the plague: the "eaten up" plague bacteria simply continue to divide inside the immune cells.

Where does the plague occur?

Nowadays the plague no longer exists in many countries. This is because the hygiene standards have improved drastically in many places. Poor hygiene, rats in houses and living in slums are possible risk factors for the development or spread of the plague. Today the plague still occurs in the following regions:

Africa (especially Central, South and East Africa)
Asia (especially Russia, Middle East, China, Southeast Asia, Myanmar)
Central and South America (tropical and subtropical regions)
North America (Southwest USA)

Plague: examinations and diagnosis

If the plague is suspected, the doctor will first take the patient's medical history (anamnesis) in conversation. For example, he asks the following questions:

What are your symptoms exactly?
How long have the complaints existed?
Have you been away recently? If so, where?
Have you had contact with rodents?
Have you noticed any insect bites?
Are you a laboratory worker at safety level S3 (these are laboratories that cultivate plague bacteria for sample analysis)?

This is followed by a physical exam. Among other things, the doctor will palpate the lymph nodes and look for swelling and pain. Sometimes the typical bumps of the bubonic plague have already formed, which is a clear indication. With pneumonic plague, the symptoms are often less clear. Cough, bloody sputum and fever can easily be misinterpreted as severe pneumonia.

For a reliable diagnosis one has to detect the plague bacterium in the body. To do this, the doctor pricks a swollen lymph node, takes a sample and sends it to the laboratory for analysis. If pulmonary plague is suspected, some sputum or a saliva sample will be sent in. In the case of a plague, the triggering bacteria can be detected in these secretions or in the sample material from the swollen lymph nodes.

In addition to this direct pathogen detection, a blood test is also important. This test can be used to determine whether the bacterium is already in the blood (see also: Plague sepsis) and whether the immune system has already recognized the pathogen.

Plague: treatment

If the diagnosis “plague” is made, the patient is isolated so that he does not infect anyone. His hospital room may only be entered under strict safety and protection regulations. Any unnecessary contact with the patient is avoided.

Nowadays the plague is treated with antibiotics, for example with streptomycin, gentamycin, tetracyclines (e.g. doxycycline) or chloramphenicol. Doctors usually first administer the drug intravenously via syringe and later in tablet form.

After starting antibiotic therapy, patients with bubonic plague must remain isolated for at least two days, and patients with pulmonary plague for at least four days

Plague: disease course and prognosis

If the bubonic plague is recognized in good time and treated consistently, the prognosis is good and almost all patients survive (mortality rate: 10 to 15 percent). Without treatment, on the other hand, 40 to 60 percent of those affected die.

With pneumonic plague and plague sepsis, the chances of survival are slim if the patient is not treated quickly. If the doctor makes the diagnosis in good time and begins antibiotic therapy, the death rate for these two forms of plague drops significantly.

After surviving the plague infection, one is largely immune to renewed infection. However, it can sometimes lead to a new illness.

The plague in the Middle Ages

The plague is one of the great infectious diseases of the Middle Ages. Colloquially it is also called the Black Death or Black Plague. The name comes from the fact that the skin can turn black and die as the disease progresses.

In the Middle Ages, large outbreaks of plague raged in Europe, claiming human lives in the hundreds of millions. But there is also evidence that the Black Death existed long before the Middle Ages. However, it is unclear whether this was really an infection with the bacterium Yersinia pestis.

Scientists today have gathered a lot of information about the plague in the Middle Ages. This makes it easy to understand the outbreak and spread of the disease at that time. In fact, there were two great waves of plague in Europe in the Middle Ages. A global pandemic followed in the 19th and 20th centuries, but Europe was largely spared. The spread and distribution of the epidemic proceeded in different ways. To date it is not clear why the further spread of the plague in Europe between the two great waves of plague did not advance for more than 700 years.

Plague pandemic 1 (approx. 541 to 750 AD): The first great wave of the plague in the Middle Ages lasted from about 540 to 750 AD. It came from Egypt across the Mediterranean to Europe and into what is now France. During this first major pandemic plague, around 100 million people died worldwide, including around half of Europe's population. There are many theories about the socio-economic as well as political consequences that this mass extinction caused in Europe. Some historians associate it with the Arab expansion towards southern Europe.

Pest pandemic 2 (14th to 19th centuries): There was a major plague outbreak in Central Asia from 1340 to 1350. The plague reached Europe and Africa again via the Silk Road trade route. The world population shrank from around 450 million to 350 million people during this period. The great wave of the plague ended only a few years after it began in Asia. However, small outbreaks continued to occur in Europe until the 19th century.

The black plague: change in medicine

The highly contagious infectious disease plague has led to a fundamental rethink in medicine. The foundations of our understanding of disease and pathways of infection today were shaped by important discoveries made during this period.

In the Middle Ages, for example, research on the dead was forbidden. Due to the large number of deaths from the plague, this general ban was slowly dissolved and the dissection of corpses was acceptable. This upheaval represents an important moment in the medical understanding of the body.

The next big step was the realization that diseases are contagious and can be transmitted through physical contact with sick people. However, it took another 200 years for this so-called contagion theory to prevail.

It was only with the third major plague in the 18th and 19th centuries that the path of transmission of the plague was finally clarified. This was due to the fact that the ecclesiastical view (plague as God's punishment) of the population was no longer sufficient alone as an explanation. This started the search for more worldly explanations. In 1894, the Swiss-French doctor and bacteriologist Alexandre Yersin succeeded in detecting the plague bacterium. In his honor it was given its scientific name: Yersinia pestis.