Diphtheria

Diphtheria is a bacterial infectious disease that is found worldwide. It only occurs rarely in Germany today thanks to protective vaccinations.

The bacteria attack the skin or the mucous membranes in the airways. They also produce a toxin that spreads throughout the body and can damage important organs.

Vaccination offers protection against diphtheria.

Types of diphtheria

There are two main types of diphtheria:

• Respiratory diphtheria (sometimes also called diphtheria of the throat or diphtheria of the upper respiratory tract): The bacteria become established in the airways and cause symptoms there. This type can be fatal – it is estimated that between 5% and 10% of people infected with respiratory diphtheria will die as a result.
• Cutaneous diphtheria (also known as diphtheria of the skin): This type can occur after small surface injuries or insect bites. It often occurs in environments with poor hygiene. Pets and farm animals can be the source of infection.

The symptoms and severity of diphtheria depend on the type of diphtheria a person has.

Symptoms of respiratory diphtheria

Respiratory diphtheria has symptoms including:

• 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 2 to 3 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 very difficult to breathe and swallow. This can be fatal in young children.

Symptoms of cutaneous diphtheria

Cutaneous diphtheria causes the following symptoms:

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

Respiratory diphtheria is caused by the bacterium corynebacterium diphtheriae. This type of bacteria is found only in humans.

Cutaneous diphtheria is caused by the bacteria corynebacterium ulcerans and corynebacterium pseudotuberculosis. In nature, both types of bacteria are only found in animals. Cutaneous diphtheria is therefore a zoonotic disease – a disease that can pass from animals to humans.

How are diphtheria pathogens transmitted?

Respiratory diphtheria is spread from person to person by means of droplet infection. In other words, if an infected person sneezes or coughs, they release droplets that contain the virus. These can be dispersed through the air and inhaled by other people. Occasionally, people contract respiratory diphtheria as a result of an infection with cutaneous diphtheria.

Cutaneous diphtheria is mainly transmitted by smear infection. For example, it can be contracted by touching the open wounds of an infected individual. However, it is also possible to contract diphtheria by touching objects that are contaminated with diphtheria pathogens. This is mainly the case in living conditions where hygiene standards are poor – for example, among homeless people.

Infections with diphtheria pathogens occur worldwide. Diphtheria is most prevalent in subtropical countries such as India. The disease also occurs in many countries in Africa, Asia, the South Pacific and Eastern Europe.

However, the serious effects of the disease have decreased significantly thanks to infant and child vaccination programs.

Cases in Germany

Diphtheria is a notifiable disease in Germany. The number of cases of cutaneous diphtheria has been increasing since 2010.

16 cases of diphtheria were reported in this country in 2020 – 15 individuals had cutaneous diphtheria, while one person had respiratory diphtheria.

The toxin produced by the diphtheria pathogens enters the bloodstream and can damage internal organs. Doctors refer to serious cases such as this as toxic diphtheria.

Possible complications include:

• blocked airways
• lung infections – ranging from pneumonia to respiratory failure
• inflammation of the cardiac muscle (myocardium)
• nerve damage (polyneuropathy)
• paralysis
• coma

To prevent diphtheria from spreading in the community, it is important for infected individuals and anyone who suspects they could be infected to isolate.

Diphtheria can be effectively prevented by vaccination. 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 diphtheria vaccine is based on the toxin produced by the pathogen that causes respiratory diphtheria. This toxin is similar to that produced by the pathogen that causes cutaneous diphtheria. However, it is not clear how effective the vaccine is against cutaneous diphtheria.

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

Recommended vaccinations

Infants should receive their first doses at the ages of 2 months, 4 months and 11 to 14 months. This is usually administered as part of the 6-in-1 vaccine, which also protects against tetanus, whooping cough (pertussis), polio (poliomyelitis), hepatitis B and infection with the haemophilus influenzae type b (Hib) bacterium.

The immunity provided by this primary immunization decreases over time. Therefore, a first booster vaccine is required between the age of 5 and 6 and a second is required between the ages of 9 and 17.

It is then recommended that people receive a booster vaccine every 10 years. Various individual and combination vaccines are available as boosters.

Do you have questions about the diphtheria vaccine and STIKO recommendations? Answers to the most frequently asked questions can be found on the Robert Koch Institute website.

Doctors typically diagnose diphtheria on the basis of a physical examination. To confirm a suspected case of diphtheria, it is important to detect the pathogen. Doctors therefore take a swab sample from the back of the throat or a wound swab and send these to a laboratory.

A bacterial culture is grown in the lab in order to detect the pathogen. It can also be detected using molecular biology-based methods, such as PCR testing. In this process, the genetic material of the bacteria (not the bacteria itself) is detected.

There is an antitoxin for the diphtheria toxin. However, the antitoxin is not effective if the toxin is already bound to the somatic cells.

For this reason, doctors will start treatment immediately if diphtheria is suspected, rather than waiting for the laboratory results.

Treatment with antitoxin

Cutaneous diphtheria of the skin is not as life-threatening as respiratory diphtheria. That is why the antitoxin is administered for diphtheria of the skin only if the wound or abscess is larger than a Euro coin and has the standard gray-brown coating.

Treatment with antibiotics

In addition to the antitoxin, doctors prescribe antibiotics to kill the living bacteria.

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 ensures that all bacteria have left the body or have been killed.

Doctors then repeat tests to determine whether the body is clear of the pathogen.

Close contacts suspected of having diphtheria are usually given antibiotics on a preventive basis. Doctors also use the term “post-exposure prophylaxis” (PEP) in this case.