Medically Reviewed By William C. Lloyd III, MD, FACS

What is diphtheria?

Diphtheria is a highly contagious, serious bacterial infection caused by Corynebacterium diphtheriae. This strain of bacteria makes a toxin that sticks to the mucous membranes of the nose, mouth and throat. The toxin forms a gray pseudomembrane over these tissues. This thick, tough coating can narrow the airway and block breathing.

Today, diphtheria is a rare disease in the United States. However, it used to be a leading cause of childhood death in this country. Up to 20% of children under the age of 5 who contracted the disease did not survive it. It also killed a high percentage of older adults. Thanks to routine vaccination against the bacterial toxin, it is no longer a significant threat to health in developed countries. In countries with poor access to vaccines, diphtheria remains a public health problem.

The main type of diphtheria is a respiratory infection. It spreads from person to person through droplets when you cough or sneeze. The infection causes a sore throat, fever, swollen lymph nodes, and malaise within five days of exposure. A less common form spreads through contact with infected skin sores. It causes skin redness, swelling and sores that may have a gray pseudomembrane.

People are at risk of getting diphtheria if they have not kept up to date on their vaccinations. The current diphtheria vaccine schedule is five doses during childhood plus a booster during adolescence. Adults should get a booster every 10 years. Living in crowded conditions further increases the risk of contracting the disease for the unvaccinated.

Diphtheria treatment requires hospitalization and isolation. Intravenous (IV) antibiotics and antitoxins will kill the bacteria and neutralize the toxin they produce. Left untreated, diphtheria can quickly cause complications, including organ damage, and become fatal. See your doctor if you are unsure of your or your child’s current vaccination status. Seek immediate medical care if you or your child become ill with signs of the pseudomembrane in the nose, mouth or throat.

What are the different types of diphtheria?

There are two types of diphtheria:

  • Respiratory diphtheria spreads through droplet transmission. It infects the upper respiratory tract, including the nose, mouth and throat. The pseudomembrane can cover the tissues in these areas.
  • Skin or cutaneous diphtheria spreads through contact with infected sores or contaminated objects. It causes a skin infection resembling similar bacterial infections, such as impetigo. The pseudomembrane can cover ulcers that develop.

What are the symptoms of diphtheria?

A hallmark symptom of diphtheria is the pseudomembrane. This is a coating that develops when the bacterial toxin cleaves an essential factor inside cells of the mucous membranes, killing the cells. The film consists of dead cells, waste products, and old white blood cells. It usually looks gray or black and may be fuzzy. In the mouth and throat, the pseudomembrane can narrow the airway and paralyze the soft palate. This can make it very noisy when people inhale. If it breaks away from the tissues, it can completely obstruct breathing.

Common symptoms of diphtheria

Diphtheria symptoms typically develop over the course of a few days. Symptoms of respiratory diphtheria include:

  • Fast heart rate
  • Swollen lymph nodes in the neck, which can cause the neck to swell dramatically (bull neck)

Sometimes, diphtheria only causes mild disease or no symptoms at all. People without symptoms are carriers that can spread the infection unknowingly.

With skin diphtheria, sores and abrasions develop on the skin. The most common sites are the arms and legs. It rarely causes serious disease.

Serious symptoms that might indicate a life-threatening condition

In some cases, the diphtheria toxin can spread through the blood and cause life-threatening complications. This includes damage to the heart, kidneys and nerves. Seek immediate medical care (call 911) if you, or someone you are with, have symptoms of diphtheria, especially the pseudomembrane. It is important to remember that a sore throat will most likely not be diphtheria unless you have not been vaccinated.

Regular medical care with immunizations is vital for preventing diphtheria and its complications.

What causes diphtheria?

Diphtheria is a bacterial infection with Corynebacterium diphtheriae. It spreads through respiratory droplets from sneezing, coughing or laughing. When someone inhales the droplets, the bacteria begin growing and multiplying in the tissues of the nose, mouth and throat.

Diphtheria spreads very easily from person to person, especially in crowded conditions. Diphtheria can also spread through contact with infected sores or contaminated objects, such as tissues, towels or countertops.

It is possible to carry diphtheria and not be sick. Carriers can pass along the infection to others who have not gotten the diphtheria vaccine. Without treatment, people remain contagious for up to four weeks.

What are the risk factors for diphtheria?

In the United States, the main risk factor for developing diphtheria is not staying current with your immunization schedule. The risk increases if you live in crowded conditions or travel to areas outside the country where diphtheria is endemic. This includes Southeast Asia and Africa.

How do you prevent diphtheria?

Preventing diphtheria relies on completing and maintaining immunization against it. There are four vaccines that immunize against diphtheria—DT, Td, DTaP, and Tdap. They combine diphtheria toxin with tetanus toxin and sometimes pertussis (whooping cough).

The current immunization schedule for diphtheria is as follows:

  • DTaP vaccine at 2, 4 and 6 months of age
  • DTaP booster between 12 to 18 months of age
  • DTaP booster between 4 to 6 years of age
  • Tdap vaccine between 11 to 12 years of age
  • Tdap or Td booster every 10 years throughout adulthood
  • Tdap during the second half of pregnancy regardless of a woman’s vaccine status

Boosters are necessary throughout your life because immunity to diphtheria fades with time. This is true even if you have had diphtheria. Your protection will wane and it is possible to get it again. As a result, boosters are necessary for people who have had the disease and recovered.

The diphtheria vaccine is a toxoid vaccine, meaning it is an inactivated toxin. It does not contain the bacteria, so these vaccines are not capable of causing the disease. Most people tolerate the vaccine well. However, mild side effects are common, such as low-grade fever and redness or tenderness at the site.

If you have been exposed to someone with diphtheria, your doctor may recommend preventive antibiotics and a booster vaccination.

How do doctors diagnose diphtheria?

The presence of the pseudomembrane is a main clue to the diagnosis of diphtheria. However, doctors will still take a throat culture to verify the presence of Corynebacterium diphtheriae. For skin diphtheria, doctors will take a sample from the skin sore for culture. Treatment will start immediately, even though culture results may not be available for a couple of days.

Your doctor may also ask several questions about your symptoms including:

  • What symptoms are you experiencing?
  • How long have you had these symptoms?
  • Are you having difficulty breathing or swallowing?
  • Does anyone you live with have similar symptoms?
  • Have you recently been around anyone with diphtheria?
  • Have you recently traveled outside the country?
  • Are you up to date with all your immunizations?
  • What other medical conditions do you have?

What are the treatments for diphtheria?

Diphtheria is a highly contagious and serious infection. It requires hospitalization for isolation and aggressive treatment. Diphtheria treatment consists of the following:

  • IV (intravenous) antibiotics to kill the bacteria 
  • IV or injections into the muscle of diphtheria antitoxin to neutralize the bacteria’s toxin
  • Isolation until the patient has had 48 hours of antibiotic therapy 

In severe cases, it may be necessary to put someone with diphtheria on a ventilator to help them breathe. They may also need other supportive treatments if diphtheria affects their heart, kidneys or nerves.

Diphtheria is a reportable disease. This means doctors and healthcare providers will need to notify their local health departments about a diphtheria infection. They will also evaluate and treat known contacts as necessary.

When doctors diagnose carriers of the disease without symptoms, they will treat them with antibiotics to clear the bacteria.

Home remedies for diphtheria

After treatment in a hospital, rest at home is an important part of recovering from diphtheria. In general, someone with diphtheria needs 4 to 6 weeks of bedrest to fully recover. If the disease involves the heart, a longer bedrest may be necessary.

What are the potential complications of diphtheria?

Respiratory diphtheria can cause airway obstruction and an inability to breathe due to the pseudomembrane. It can also lead to complications when the toxin spreads through the blood to organs. These complications can be serious and include:

  • Myocarditis, which is damage to the heart muscle that can lead to heart failure
  • Polyneuropathy, which is nerve damage. It can affect the nerves that control breathing and nerves in the throat, arms and legs, leading to muscle weakness in these areas.

Respiratory diphtheria can be fatal. Left untreated, about half of people with diphtheria will die. Even with treatment, up to 10% of people worldwide do not survive. Children and the elderly are more likely to die from the disease.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jun 2
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