Diphtheria

Diphtheria is a serious bacterial infection that can affect your throat, nose, and sometimes skin, creating a thick coating that can block your airway and spread toxins throughout your body.

Table of contents

• What is diphtheria
• Types of diphtheria
• What causes diphtheria
• How diphtheria spreads
• Symptoms
• Complications
• Who is at risk
• Diagnosis
• Treatment
• Prevention

What is diphtheria

Diphtheria is a contagious disease caused by bacteria that produce a harmful substance called a toxin (a poison produced by living organisms). This infection usually affects the mucous membranes (the moist lining) of the nose and throat, though it can also affect the skin and other parts of the body^[1][2].

The disease is extremely rare in the United States and other developed countries because of widespread vaccination against it. However, many countries with limited healthcare or vaccination programs still experience outbreaks of diphtheria^[1][4].

Diphtheria can be treated with medications, but in advanced stages it can damage the heart, kidneys, and nervous system. Even with treatment, diphtheria can be deadly, especially in children. For unvaccinated individuals, without proper treatment, diphtheria can be fatal in around 30% of cases, with young children at higher risk of dying^[1][4].

• Nose
• Throat
• Tonsils
• Larynx (voice box)
• Skin
• Heart
• Kidneys
• Nerves

Types of diphtheria

There are two main types of diphtheria^[2]:

Classical respiratory diphtheria is the most common and serious type. It affects your nose, throat, tonsils, or voice box. This type occurs when toxin-producing bacteria infect the upper respiratory tract^[2][3].

Skin diphtheria (also called cutaneous diphtheria) causes skin infections with painful open sores or ulcers, rashes with scales or peeling skin, and swelling near the affected area. Ulcers may be covered by a gray membrane. Although it’s more common in tropical climates, this type can also occur in areas with poor hygiene and crowded conditions^[1][2].

What causes diphtheria

Diphtheria is caused by a bacterium called Corynebacterium diphtheriae. Not all strains of this bacterium cause disease—only those that produce diphtheria toxin are dangerous. The bacteria must carry a specific piece of genetic information (called the tox gene) and express it to produce the toxin^[3][7].

When toxin-producing bacteria infect your body, they stick to the lining of your airways. There they release toxin that damages and kills healthy tissue cells. Within a few days, a thick, gray or black coating (called a membrane) forms over the infected area. This membrane can cover tissues in your throat, tonsils, nose, and voice box. The toxin can also spread through your bloodstream and damage other organs in your body^[2][3].

Different strains of Corynebacterium diphtheriae have been identified, including gravis, intermedius, and mitis. All three strains can produce toxins, though intermedius is thought to be most often associated with the toxin that causes severe disease^[7].

How diphtheria spreads

Diphtheria spreads from person to person, most commonly through respiratory droplets. When an infected person coughs or sneezes, they release tiny droplets containing bacteria into the air. Other people can get infected if they breathe in those droplets^[2][3].

You can also get diphtheria by touching something that has bacteria on it, such as items soiled with discharge from an infected person. With skin diphtheria, direct contact with infected open sores or ulcers can spread the infection^[2][3].

Some people carry diphtheria bacteria without showing any symptoms. These individuals are called carriers, and they can spread the infection to others without knowing they are sick. In some people, infection causes only a mild illness or no obvious signs at all^[1][2].

After exposure to the bacteria, symptoms usually begin 2 to 5 days later, though this can range from 1 to 10 days. Without antibiotic treatment, an infected person can remain contagious for 2 to 6 weeks^[1][2][7].

Symptoms

Diphtheria signs and symptoms usually begin 2 to 5 days after a person becomes infected^[1].

In respiratory diphtheria, common symptoms include^[1][2]:

• A thick, gray or white membrane covering the throat and tonsils
• Sore throat and hoarseness
• Swollen glands (enlarged lymph nodes) in the neck
• Difficulty breathing or rapid breathing
• A harsh or high-pitched breathing sound due to narrowing of the upper airways
• Nasal discharge
• Fever and chills
• Tiredness and weakness
• Difficulty swallowing

In some cases, the thick membrane in the throat can block the airway, creating a barking cough similar to what is seen in croup. This membrane is what makes diphtheria different from other more common infections that cause sore throat, such as strep throat^[1][6].

With skin diphtheria, symptoms can include^[1][2]:

• Painful open sores or ulcers
• Rash with scales or peeling skin
• Swelling and discoloration near the sore or rash
• Yellow spots or sores on the skin
• Pus-filled blisters on legs, feet, and hands

Complications

Diphtheria can lead to serious, potentially life-threatening complications. These complications are caused by the diphtheria toxin spreading through the bloodstream and affecting other organs in the body^[1][2].

Complications can include^[1][2][6]:

• Airway blockage, which can cause suffocation if the membrane blocks breathing
• Heart damage, including inflammation of the heart muscle (myocarditis) or congestive heart failure, which can result in abnormal heart rate
• Nerve damage (inflammation of nerves), which can result in paralysis depending on which nerves are affected
• Kidney problems and kidney failure
• Bleeding problems due to low levels of platelets (blood cells that help with clotting)

Up to 50% of people whose diphtheria isn’t treated may die. Even with treatment, around 10% of people with diphtheria will die from the disease^[1][7].

Who is at risk

The main risk factor for getting diphtheria is not being vaccinated against it or not having received a booster shot. A lack of the diphtheria vaccine or not having up-to-date vaccinations are the primary risk factors for developing severe diphtheria symptoms^[2][3].

Other factors that increase the risk of severe disease include^[2][7]:

• Having a weakened immune system
• Being under age 5 or over 40
• Overcrowding and poor living conditions
• Poor hygiene
• Not being well nourished

Risk factors for exposure include^[2][3]:

• Close contact with someone who has diphtheria, including living with them, being close together often, or sharing respiratory secretions
• International travel to areas where diphtheria is common, such as parts of Africa, South America, India, Southeast Asia, and Eastern Europe
• Low vaccination rates in the community
• Living or working in overcrowded places

Nearly all diphtheria cases in the United States are associated with international travel^[3].

Previous infection may not protect against getting diphtheria again. Without vaccination, you can get diphtheria more than once^[2][6].

Diagnosis

Healthcare providers usually diagnose diphtheria based on looking for common signs and symptoms. Doctors may suspect diphtheria in a sick person who has a sore throat with a gray membrane covering the tonsils and throat^[1][2][10].

To confirm the diagnosis, a doctor will use a swab to take a sample from the back of the throat (or from a skin sore if cutaneous diphtheria is suspected). The sample is then sent to a laboratory to test for the presence of Corynebacterium diphtheriae bacteria^[2][3].

Laboratory testing involves trying to grow (culture) the bacteria. If Corynebacterium diphtheriae bacteria grow, further testing is needed to determine whether the strain produces diphtheria toxin. This is the only way to confirm that a patient has diphtheria. However, growing bacteria takes time^[3].

Because diphtheria is a serious illness, if a healthcare provider suspects respiratory diphtheria, treatment will be started right away without waiting for test results^[3][10].

Treatment

Diphtheria is a serious illness that doctors treat immediately and aggressively. Treatment should begin even before laboratory test results confirm the diagnosis^[10][11].

Doctors first ensure that the airway isn’t blocked or reduced. In some cases, they may need to place a breathing tube in the throat to keep the airway open until inflammation decreases. In severe cases, surgery may be done to create an opening in the windpipe (called a tracheostomy) for severe breathing problems^[10][14].

The main treatments for diphtheria include^[9][10][11]:

Antibiotics help kill the bacteria in the body and clear up the infection. Only erythromycin or penicillin is recommended for diphtheria. Antibiotics lessen the time that someone with diphtheria is contagious. Treatment usually lasts about 2 weeks^[9][10][11].

Diphtheria antitoxin is a medication that counteracts the diphtheria toxin in the body. This medicine is injected into a vein or muscle. The antitoxin stops the toxin from causing more damage to the body, but it must be given before the toxin enters cells. Before giving an antitoxin, doctors perform skin allergy tests to make sure the patient doesn’t have an allergy to it. Antitoxin is recommended for respiratory diphtheria but isn’t typically needed for cutaneous diphtheria^[3][10][11].

In the United States, healthcare providers can obtain diphtheria antitoxin from the Centers for Disease Control and Prevention on request^[10][11].

People with diphtheria often need to be in the hospital for treatment. They may be isolated in an intensive care unit because diphtheria can spread easily to anyone not vaccinated against the disease^[10].

Doctors monitor patients closely for complications, including checking cardiac and neurologic status due to the risk of developing myocarditis and nerve damage^[11].

Any infected skin wounds should be thoroughly cleaned if you have skin diphtheria. Skin ulcers usually heal within 2 to 3 months but may leave a scar^[9].

People who have been in close contact with someone who has diphtheria will also need to take antibiotics and may be given the diphtheria vaccine. A contact tracing team will get in touch with anyone who needs to be treated^[9][11].

Prevention

The best way to prevent diphtheria is to get vaccinated. Vaccination can prevent diphtheria, and diphtheria vaccines are very effective. Being vaccinated is the best protection against diphtheria^[3][4][9].

There are three types of combination vaccines that include protection against diphtheria^[23]:

• DTaP vaccine for babies and children (also protects against tetanus and whooping cough)
• Tdap vaccine for preteens, teens, and adults (also protects against tetanus and whooping cough)
• Td vaccine for adults (also protects against tetanus)

The vaccination schedule recommended by health authorities includes^[9][23]:

• DTaP vaccines at 2, 4, and 6 months of age (three separate doses)
• A booster dose given at 12 to 18 months
• A booster dose given again at 4 to 6 years (before starting school)
• Tdap vaccine given at 11 to 12 years
• Booster shots of Tdap or Td every 10 years after that to maintain protection
• Tdap vaccine during the second half of each pregnancy for all pregnant women

Although vaccination is not guaranteed to prevent diphtheria, vaccinated people who later develop diphtheria have been reported as having milder and fewer fatal infections. Diphtheria might not confer immunity, so all patients recovering from diphtheria should be confirmed to be up to date with their vaccinations^[7][11].

Most people who get a vaccine that helps protect against diphtheria don’t have any serious problems. Side effects are usually mild and go away on their own within a few days. These can include swelling or soreness where the vaccine was given, mild fever, tiredness, headache, or irritability^[23].

If you’re traveling to a part of the world where there may be a risk of diphtheria, you may need a booster vaccination if you were last vaccinated against it more than 10 years ago. Some parts of the world where there may be a risk include Africa, South America, India, Southeast Asia, and Eastern Europe^[9].

Close contacts of someone with diphtheria should receive antibiotics to prevent them from getting sick. They should also be monitored for illness, tested for diphtheria, and vaccinated if their diphtheria vaccines aren’t up to date^[3][11].