Diphtheria is a serious and contagious infection caused by the bacteria Corynebacterium diphtheriae. Diphtheria can lead to paralysis, heart failure, and difficulty breathing. In some cases, it can be fatal.

The Centers for Disease Control and Prevention (CDC) state that the hallmark sign of diphtheria is a sheet of grayish material covering the back of the throat. Though rare in the United States, countries reported more than 16,000 cases worldwide in 2018.

Without treatment, diphtheria can be fatal for up to 50% of people. Vaccinations in the U.S. have helped significantly reduce the threat of a person contracting diphtheria. However, doctors may still recommend treatment for people who have come in close contact with those who have it.

This article will provide information on what diphtheria is and what causes it. It will also look at symptoms a person can expect, treatment options available, and how a person can help prevent contracting the bacteria.

In addition, this article will outline how doctors diagnose the condition and the potential complications that may occur.

A person vaccinating a child against diphtheria.Share on Pinterest
A health worker applies a vaccine against diphtheria to a baby in Lima, on October 28, 2020, after a case was detected at a popular district. LUKA GONZALES/Getty Images

Diphtheria is a highly contagious bacterial infection that occurs due to variants of Corynebacterium diphtheriae (C. diphtheriae).

It typically affects the respiratory system or the integumentary system. The integumentary system includes the three layers of the skin — the hypodermis, dermis, and epidermis — and the glands, nails, and hair.

Symptoms typically include a thick, gray coating in the nose and throat along with a sore throat, swollen glands, weakness, and mild fever. If the condition affects the skin, ulcers and open sores can appear.

According to a 2019 article, some variants of this bacterium produce a toxin called an exotoxin. This causes the most serious complications associated with diphtheria. The toxin inhibits the production of proteins and leads to cell and tissue death.

If the toxin enters the bloodstream, it can damage the kidneys, heart, and nerves. A person can develop myocarditis, which is the inflammation of the heart muscles, and neuropathy. Neuropathy is nerve damage that can result in numbness, muscle weakness, pain, and tingling sensations.

Other variants of C. diphtheriae do not produce the toxin. This results in less severe disease, typically causing a sore throat and, in rare cases, pharyngitis.

In some cases, variants can also result in bacteremia and endocarditis. Bacteremia is the presence of bacteria in the blood. Endocarditis is the inflammation, and sometimes the infection, of the inner lining of the heart chambers and valves.

Routine immunization in the U.S. and other parts of the world has significantly reduced the risk of diphtheria exposure in the U.S.

Diphtheria is an infectious disease that occurs due to C. diphtheriae. It is the toxin this bacterium produces that causes people to become very ill.

How does a person contract diphtheria?

A person can contract diphtheria from direct physical contact with:

  • respiratory droplets from coughing or sneezing
  • secretions from the nose and throat, such as mucus and saliva
  • infected skin lesions

The infection can transmit from a person with the infection to any mucous membrane in another person.

Specific signs and symptoms of diphtheria depend on the particular variant of bacteria involved and the part of the body affected. Diphtheria can affect the respiratory system or cause a skin infection.

According to the CDC, if it has affected the skin, a person can develop open sores and ulcers. This rarely results in severe disease.

The incubation period is typically 2–5 days, but can take up to 10 days.

Respiratory diphtheria can develop gradually, resulting in:

  • difficulty swallowing
  • sore throat
  • weakness
  • swollen glands in the neck
  • mild fever
  • appetite loss
  • hoarseness, if the disease has affected the larynx

After 2–3 days, the released toxin kills the healthy tissue in a person’s respiratory system. This results in a thick, gray coating that develops in the nose or throat. Doctors refer to this coating as a pseudomembrane.

If the membrane extends to the larynx, hoarseness and a barking cough become more likely, as does the danger of complete obstruction of the airway. The membrane may also extend farther down the respiratory system toward the lungs.

Potentially life threatening complications can occur if the toxin enters the bloodstream and damages other vital tissues.

Some potential complications include:

In some cases, diphtheria can be fatal. Overall, 5–10% of people who contract the infection will die.

Less severe disease in other locations

If the bacterial infection affects tissues other than the throat and respiratory system, such as the skin, the illness is generally milder. This is because the body absorbs lower amounts of the toxin, especially if the infection only affects the skin.

The infection can coexist with other infections and skin conditions and may look no different from eczema, psoriasis, or impetigo. However, diphtheria in the skin can produce ulcers with no skin at the center, clear edges, and sometimes grayish membranes.

Other mucous membranes can become infected with diphtheria, including the conjunctiva of the eyes, vaginal tissue, and external ear canal.

If a doctor suspects diphtheria, they can order a test to confirm the diagnosis. Tests involve swabbing the back of the throat or an ulcer on the skin and then attempting to grow a culture.

Often, they can determine if the person has diphtheria through examining signs and symptoms.

Since bacterial cultures can take some time to grow, a doctor who suspects diphtheria may recommend starting treatment right away.

Treatment aimed at countering the bacterial effects has two components:

  • Antitoxin: This is also known as anti-diphtheritic serum. It neutralizes the bacteria’s toxins. Doctors use the antitoxin to treat diphtheria that has affected the respiratory system.
  • Antibiotics: Erythromycin or penicillin can eradicate the bacteria and stop them from spreading. Antibiotics can treat diphtheria affecting the respiratory system and skin.

Early treatment with antitoxin is important, and doctors typically start it before the culture comes back. The antitoxin only works on toxins that have not yet bound with cells and tissue in the body.

People are no longer contagious after taking antibiotics for 48 hours. However, it is important that a person finishes the full course of antibiotics.

One of the most effective methods of diphtheria prevention is vaccination. Many countries, including the U.S., use routine vaccines to help prevent diphtheria infection.

Pharmacists derive vaccines from a purified toxin removed from a variant of the bacterium.

There are four vaccines that can help to protect against diphtheria, which include:

  • DTaP: This protects against diphtheria, tetanus, and pertussis.
  • DT: This protects against diphtheria and tetanus.
  • Tdap: This protects against diphtheria, tetanus, and pertussis.
  • Td: This protects against diphtheria and tetanus.

Modern vaccination schedules include diphtheria toxoid as a childhood immunization, known as diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP).

The CDC recommends DtAP for those under the age of 7 years. Infants should receive five doses of DTap at the following ages:

  • 2 months
  • 4 months
  • 6 months
  • 15–18 months
  • 4–6 years

Those ages 11–13 years should receive the Tdap shot, and adults should receive the Td or Tdap every 10 years.

Diphtheria is a bacterial infection that can lead to severe complications, including death. In the U.S., the condition is now rare due to access to vaccinations that help prevent it.

Symptoms of diphtheria include a thick, gray coating at the back of the throat, along with weakness, a sore throat, swollen glands in the neck, and mild fever.

If diphtheria affects the skin, a person may develop ulcers and open sores.

If a person presents with symptoms of diphtheria, a doctor can often diagnose the condition with an examination and a bacterial culture. Early treatment can help prevent major complications.

The best form of prevention is vaccination.