Diphtheria is an infectious disease caused by corynebacteria. It creates a gray-brown coating on the tonsils. The disease can lead to respiratory issues, heart failure, paralysis, and even death.

At a glance

  • Diphtheria is a potentially life-threatening infection caused by corynebacteria, which produces the diphtheria toxin.
  • Corynebacterium (C.) diphtheriae causes diphtheria of the throat and larynx, and toxic diphtheria.
  • In addition to C. diphtheriae, the bacteria strains C. ulcerans and C. pseudotuberculosis can cause diphtheria of the skin.
  • The disease is treated with an antitoxin and antibiotics.
  • An effective vaccine for diphtheria exists.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Ein Junge bekommt eine Impfung in den Oberarm.

What is diphtheria?

Diphtheria is a potentially life-threatening infectious disease caused by a toxin produced by bacteria called corynebacteria. The classic pathogen is Corynebacterium (C.) diphtheriae, which causes throat, larynx, and toxic diphtheria. In addition to C. diphtheriae, the bacteria strains C. ulcerans and C. pseudotuberculosis can cause diphtheria of the skin.  

Diphtheria can lead to death. Even when treated, approximately one in ten infected with the disease dies. Without treatment, up to half of patients die from the disease.

What are the symptoms of diphtheria?

Bacteria that cause diphtheria of the throat settle in the respiratory tract. There they produce a toxin (“diphtheria toxin”) that can cause the following symptoms: 

  • weakness
  • sore throat
  • fever
  • difficulty swallowing
  • barking cough (croup cough)
  • wheezing and shortness of breath
  • hoarseness to complete loss of the voice
  • swollen lymph nodes in the throat
  • sweet-smelling, offensive breath odor
  • bluish-red discoloration of the skin (cyanosis)
  • restlessness and anxiety
  • paleness

The toxin destroys healthy tissue in the respiratory tract. Within two to three days, the dead tissue forms a thick, gray-brown coating, which can then accumulate in the throat or nose. Doctors call this coating a pseudomembrane. It can cover tissue in the nose, on the tonsils and larynx, and in the throat, making it difficult to breathe and swallow. 

Skin or wound diphtheria often appears after small superficial injuries or insect bites. It manifests itself through the following symptoms: 

  • swelling
  • redness
  • wounds that have a punched-out appearance
  • slimy coating

The toxin can also enter the blood stream and damage internal organs. This can lead to further complications. They include: 

  • blocked airways
  • lung infection (from pneumonia to respiratory failure)
  • damage to the cardiac muscle (myocardium)
  • nerve damage (polyneuropathy)
  • paralysis
  • coma

What causes diphtheria?

Diphtheria of the nose, throat, larynx, or toxic diphtheria are caused by C. diphtheriae. This bacteria is found only in humans. The disease has different names and was considered a major cause of death in children at the start of the 20th century. It causes a gray-brown coating to form on the back of the throat. The Greek word diphtéra basically means a “pair of leather rolls” and refers to the brown coating. The disease is also designated as genuine croup cough. This name originates from the Scottish word croup, which means hoarseness.

C. ulcerans and C. pseudotuberculosis cause diphtheria of the skin. The disease appears in the form of skin wounds that have a punched-out appearance and a slimy coating. In nature, these two bacteria are found only in animals. Diphtheria of the skin thus is a zoonosis, meaning a disease that has been transferred from animals to humans. 

Diphtheria of the nose, throat, larynx or toxic diphtheria is transmitted from human to human, mainly through respiratory droplets produced by coughing or sneezing. In rare cases, a human can contract the disease by touching an open wound. A person can also contract diphtheria by touching an object on which the bacteria that causes diphtheria is found. Medical professionals call cases such as these a smear infection. It is the main channel of transmission for diphtheria of the skin. Diphtheria of the skin that is caused by C. diphtheriae can also be transmitted and lead to diphtheria of the nose, throat, larynx or toxic diphtheria.

How common is diphtheria?

C. diphtheriae infections can be found worldwide, however serious effects of the disease have decreased significantly due to infant and child vaccination programs. The last major epidemic in Germany occurred during World War II. From a world view, the last epidemic was in Russia in the mid-90s. After the fall of the Soviet Union, the immunization rate fell below 80 percent.

Im Jahr 2020 wurden in Deutschland 16 Fälle von Diphtherie gemeldet.

Since 2010, cases of diphtheria of the skin caused by C. ulcerans and C. pseudotuberculosis have risen. In 2018, 26 cases of diphtheria were reported in Germany; 25 were diagnosed as diphtheria of the skin and one as diphtheria of the throat.

How can diphtheria be prevented?

A vaccination is an effective way to prevent diphtheria. The vaccine targets the toxin, not the bacteria. This is why the pathogen can multiply in the body and sometimes trigger symptoms, such as fever or general weakness, even if a vaccine has been administered.

The vaccine targets the toxin produced by C. diphtheriae. However, there are some differences between it and the toxin produced by C. ulcerans. Therefore, it is not completely clear how effective the vaccination is against this pathogen.

The Standing Committee on Vaccination in Germany (Ständige Impfkommission, STIKO) recommends that all babies, children, adolescents and adults be vaccinated against diphtheria as standard.

The Standing Vaccination Committee (STIKO) at the Robert Koch Institute recommends that all infants, children, youth, and adults be vaccinated against diphtheria.  

Infants should receive their first doses at the ages of 2, 4, and 11 to 14 months. They provide basic immunization. The inoculation protection decreases over time. Therefore, a booster vaccination should be administered again at the ages of 5 to 6 years and 9 to 17 years.  

STIKO recommends that adults receive a booster every 10 years. This vaccine is most often administered in combination with tetanus, pertussis and polio. 

How do vaccinations work?

The video below explains how a vaccination works.

This and other videos can also be found on YouTube

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How is diphtheria diagnosed?

Doctors typically use the aforementioned symptoms to diagnose diphtheria. Additionally, the back of the throat is swabbed if diphtheria is suspected. The sample is tested for the bacteria that causes diphtheria.  

They can also take a sample from a wound. The lab then tries to grow a culture of the bacteria. If the bacteria grows, the doctor can be certain that the person has diphtheria. These labs can also use a molecular biological method, such as PCR, to detect the pathogen. In this process, the genetic material of the bacteria (not the bacteria itself) is detected.

How is diphtheria treated?

There is an antitoxin for the diphtheria toxin. However, the antitoxin is not effective if the toxin is already bound to the somatic cells. That is why medical professionals do not wait for lab results if diphtheria is suspected. They start treating patients immediately. In addition to the antitoxin, doctors prescribe antibiotics to kill the living bacteria.

Since the antitoxin is typically taken from horses and some people have an allergic response to it, complications can arise. In a worst-case scenario, the antitoxin can even trigger anaphylactic shock. This is a life-threatening allergic reaction. Therefore, patients being treated for suspected diphtheria are sent to intensive care where they can be artificially ventilated and conditions such as heart failure or possible cardiac arrhythmia can be treated. 

Important: People diagnosed with diphtheria are typically no longer contagious 48 hours after the start of antibiotic treatment. However, it is important that they continue with antibiotic treatment, typically for two weeks. This helps the attending physician ensure that all bacteria have left the body or have been killed. The test is repeated after treatment. The doctors test for any remaining pathogen in the body. However, antibiotics do not impact the course of the disease; only antitoxins are effective for this.

Diphtheria of the skin is not as life-threatening as diphtheria of the throat. Since the toxin binds to somatic cells, it is improbable that it would spread throughout the body. That is why the antitoxin is administered for diphtheria of the skin only if the wound or abscess is larger than a Euro coin (approximately two square centimeters) and has the standard gray-brown coating.

Reviewed by the German Society for Pediatric Infectiology (Deutsche Gesellschaft für Pädiatrische Infektiologie e.V.).

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