Bubonic plague

Plague is a life-threatening infectious disease caused by bacteria called Yersinia pestis. In the past, it was known as the “Black Death”.

There are three different forms of plague: 

• Bubonic plague: This is the most common form of plague worldwide. 
• Pneumonic plague: This can occur independently of bubonic plague or as a result of it. 
• Septicemic plague: This can occur when the infection spreads through the entire body. 

A typical symptom of bubonic plague is the swellings (buboes) that occur, usually in the groin area, as a result of enlarged lymph nodes.

If the pathogen reaches the lungs of a person with bubonic plague, this is known as secondary pneumonic plague. 

How great is the risk of contracting the disease? 

There is no risk of contracting plague in Germany or the rest of Europe. However, it still occurs in tropical and subtropical regions – particularly in rural areas. Individual outbreaks occasionally occur, increasing the risk of infection. 

Anyone traveling to and spending time outdoors in regions where plague is still present should follow the rules on hygiene and take particular care in relation to contact with rats and other rodents. 

The incubation period of bubonic plague, i.e. the time between getting infected and the first symptoms appearing, is one to seven days.

The symptoms of bubonic plague occur very suddenly.

The general symptoms include:

• fatigue
• headache
• vomiting
• high temperature, fever
• chills
• impaired consciousness
• liver and spleen enlargement

The typical sign of bubonic plague is swelling caused by enlarged lymph nodes. These swellings, known as buboes, can rupture, releasing a highly contagious pus. Flea bites can sometimes be seen some distance away from the buboes. 

Bubonic plague is caused by a type of bacteria called Yersinia pestis. This infectious agent (pathogen) is highly contagious and can be spread through contact with animals or person-to-person contact. 

Infection through contact with animals 

The pathogen is usually transmitted by a bite from infected fleas. These fleas live primarily on host animals such as rats and other rodents.

However, the pathogen that causes plague can also be spread to humans through direct contact with dead wild animals – for example, when infected animal secretions are touched.

Infection through person-to-person contact

It is possible for bubonic plague to be spread from person to person through contact with pus from the buboes (this is known as “smear infection”, i.e., infection by touch).

If a person catches bubonic plague and the bacteria spread to the lungs, pneumonic plague develops there. If this happens, the person can infect others directly through tiny droplets containing the pathogen, which are released into the air when they cough or sneeze, for example.  

A total of 3,248 cases of plague in all its forms worldwide were reported to the World Health Organization (WHO) between 2010 and 2015. Of these, 584 infections proved fatal. 

In Germany, no plague infections have been registered over the last few centuries, not even by people entering the country.

In which countries does plague still occur?

The countries in which plague is endemic, i.e. present on a continuous basis, include:

• Democratic Republic of the Congo
• Madagascar
• Peru 

Rare cases of plague are also known to occur in countries including: 

• China 
• India 
• Malawi 
• Mozambique 
• Zimbabwe 
• Tanzania 
• Vietnam 
• Uganda 

The USA is the only country outside the subtropics and tropics where plague is present.  

The Plague Map of the World Health Organization (WHO) provides a complete overview of the regions where plague can occur. 

Bubonic plague develops following a bite from an infected flea.

When a person is bitten, the pathogen enters under the skin. It then travels through the lymphatic system to the nearest lymph node, which becomes painfully inflamed, enlarged and swollen. The lymph nodes most commonly affected are those in the groin.

Without treatment, bubonic plague can lead to death within 24 hours. This happens in around half of all people infected. If it is treated with antibiotics, around 90 percent of those infected survive.

What are the complications associated with bubonic plague?

An infection of the lungs is a complication of bubonic plague. Symptoms of secondary pneumonic plague appear around five to seven days after the initial infection.

In rare cases, an infection can cause inflammation of the meninges (the layers of membrane protecting the brain) or the pathogen may spread through the bloodstream, causing potentially fatal sepsis. 

At present, no vaccine to prevent plague has been approved anywhere in the world. Under certain circumstances, people who come into contact with others who have plague may take an antibiotic as a precaution.

Those traveling in countries with cases of plague should avoid contact with potentially infected animals. These include rats and other rodents in particular. 

The Foreign Office has published a leaflet about plague, aimed at people working in and traveling to affected areas. Link to the leaflet

Initial indications of bubonic plague are detected when doctors take a detailed medical history of the patient. First, the doctor asks the patient, for example:

• whether they have stayed in an at-risk area in recent days 
• where there are currently any known plague infections in the at-risk area 
• whether the patient has had any contact with people who have plague

If the doctor determines, when taking the patient history, that the patient has been exposed to an increased risk of infection and if additional symptoms (such as flea bites) are present, this corroborates the suspicion of an infection with bubonic plague.

To enable an accurate diagnosis, doctors take samples from the lymph nodes, blood or saliva for laboratory testing.

In the lab, the bacteria cells are grown and analyzed (bacteria culture test). Alternatively, the pathogens may be detected immediately via genetic analysis using PCR testing.

Anyone infected with plague must be admitted to hospital and treated with suitable antibiotics as soon as possible.

Treatment should begin within 18 hours of the first symptoms occurring.

It is important to determine at an early stage of the treatment process whether the selected drugs are fighting the pathogen effectively. This is because a number of infectious agents have now developed resistance to antibiotics.