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., high fever, chills, swollen lymph nodes, black/bluish skin coloration, bloody sputum.
- Cause: Trigger is the bacterium Yersinia pestis, which is transmitted by flea bites and can also be passed from person to person. Rarely, infection occurs through direct contact with infected rodents. For pneumonic plague, droplet infection is the main route of transmission. Risk factors include poor hygiene standards.
- Treatment: antibiotics
- Prognosis: good if therapy is started early, otherwise the disease is usually fatal.
Plague: Description
People infected with plague can also 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 plague-infected wild rodents. However, according to the Robert Koch Institute, this is now only the case in limited endemic areas in Africa, Asia, tropical Central and South America, and the southwestern United States. The spread of plague is favored when many people live together in a confined space under poor hygienic conditions.
However, major epidemics and pandemics that claimed millions of victims in the Middle Ages no longer occur today.
Along with cholera, smallpox and yellow fever, plague is one of the four quarantine diseases as defined by the World Health Organization (WHO). These diseases have a particularly threatening course and are extremely contagious.
Plague: Symptoms
The 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 plague in humans, some with different plague symptoms.
Bubonic plague
Bubonic plague, also called bubonic plague or black death, is the most common and best known form of plague. It is generally transmitted only by flea bites. Usually, the first symptoms appear two to six days after infection.
- high fever
- chills
- headache
- general feeling of weakness
As with a bruise, the lymph node swellings turn blue within a few days, creating the typical image of dark bumps in plague patients. Rarely, they open and discharge highly infectious secretions.
If the lymph nodes bleed in, complications can arise. This is because there is then a risk of bacteria getting into the blood or lungs. Then a so-called plague sepsis or pneumonic plague can result. Both forms of the disease are serious and often fatal.
Pneumonic plague
Pneumonic plague develops either as a complication of bubonic plague or as an “independent” disease after transmission of the plague pathogen via droplet infection: sick people spread 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 inhale them, the bacteria enter the lungs directly and trigger pneumonic plague.
Plague sepsis
In about ten percent of all cases, the plague bacteria enter the blood and cause “blood poisoning.” This so-called plague sepsis occurs as a complication of bubonic or pneumonic plague. Possible symptoms include falling blood pressure, high fever, confusion or lethargy, and digestive problems.
Because the pathogens can spread anywhere in the body via the blood, the consequences of plague sepsis are varied and can affect different organs. Particularly dangerous are clotting disorders, because they are associated with bleeding inside the body. Other possible consequences include heart failure, enlargement of the spleen and liver, and kidney failure.
If left untreated, plague sepsis leads to circulatory failure. If blood flow in the body cannot be maintained, the patient will die from plague sepsis.
Plague: causes and risk factors
The plague bacterium is highly contagious. It can also trick the human immune system with a special mechanism: Important defense cells of the immune system are certain white blood cells. They can “eat up” invaders such as bacteria and thus stop an infection. Not so with plague: the “eaten up” plague bacteria simply continue to divide inside the defense cells.
Where does the plague occur?
Nowadays, plague no longer exists in many countries. This is because hygiene standards have improved dramatically in many places. Lack of hygiene, rats in the house and living in slums are possible risk factors for the development and 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 (southwestern USA)
Plague: investigations and diagnosis
- What exactly are your symptoms?
- How long have the symptoms been present?
- Have you traveled recently? If so, where to?
- Have you had any contact with rodents?
- Have you noticed insect bites on you?
- Are you a safety level S3 laboratory worker (these are laboratories that grow plague bacteria for sample evaluation)?
This is followed by a physical examination. Among other things, the doctor will palpate the lymph nodes, looking for swelling and pain. Sometimes the typical bumps of bubonic plague have already formed, which is a clear indication. In pneumonic plague, the symptoms are often less clear. Cough, bloody sputum, and fever can easily be misinterpreted as severe pneumonia.
For a definite diagnosis, the plague bacterium must be detected 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 pneumonic plague is suspected, some sputum or a saliva sample is sent in. In the case of plague, the bacteria that cause the disease can be detected in these secretions or in the sample material from the swollen lymph nodes.
Plague: Treatment
Once the diagnosis of plague is made, the patient is isolated so that he does not infect anyone else. His hospital room may only be entered under strict safety and protection regulations. Any unnecessary contact with the patient is avoided.
Nowadays, plague is treated with antibiotics, for example streptomycin, gentamycin, tetracyclines (e.g. doxycycline) or chloramphenicol. Doctors usually administer the medication first intravenously via injection, and later in tablet form.
After starting antibiotic therapy, patients with bubonic plague must remain isolated for at least two days, patients with pneumonic plague for at least four days.
Plague: course of the disease and prognosis
If bubonic plague is detected in time and treated consistently, the prognosis is good and almost all patients survive (mortality rate: 10 to 15 percent). In contrast, without treatment, 40 to 60 percent of those who contract the disease die.
In pneumonic plague and plague sepsis, the chances of survival are low if patients are not treated quickly. However, if the doctor makes the diagnosis in good time and starts antibiotic therapy, the mortality rate for these two forms of plague drops significantly.
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 in the course of the disease, the skin turns black and dies.
In the Middle Ages, major plague outbreaks ravaged Europe, claiming lives in the hundreds of millions. However, there is also evidence that the Black Death existed long before the Middle Ages. However, it is unclear whether it was really an infection with the bacterium Yersinia pestis.
Plague Pandemic 1 (ca. 541 to 750 AD): The first major wave of plague in the Middle Ages lasts from about 540 to 750 AD. It spread from Egypt across the Mediterranean Sea to Europe as far south as present-day France. During this first major plague pandemic, about 100 million people died worldwide, including about half of the European population. There are many theories about the socioeconomic and political consequences of this mass death in Europe. Some historians link it to Arab expansion toward southern Europe.
Plague Pandemic 2 (14th to 19th centuries): Between 1340 and 1350, there was a major plague outbreak in Central Asia. The plague again reached Europe and Africa via the Silk Road trade route. The world population shrank from about 450 million to 350 million people during this time. The great wave of plague did end a few years after it began in Asia. However, small outbreaks continued to occur in Europe until the 19th century.
The black plague: changes in medicine
In the Middle Ages, for example, research on the dead was forbidden. However, due to the many plague deaths, this general prohibition was slowly lifted and dissection of corpses became acceptable. This upheaval represents an important moment in the medical understanding of the body.
The next major step was the realization that diseases could be contagious and transmitted through physical contact with sick people. However, it took another 200 years for this so-called contagion theory to become established.
It was not until the third great plague in the 18th and 19th centuries that the way in which the plague was transmitted was finally clarified. This was due to the fact that the ecclesiastical view (plague as God’s punishment) was no longer sufficient as the sole explanation for the population. This set in motion the search for more secular explanations. In 1894, the Swiss-French physician and bacteriologist Alexandre Yersin succeeded in detecting the plague bacterium. In his honor, it was given its scientific name: Yersinia pestis.
