Diphtheria – Causes, Signs and symptoms


Also called: Diphtheria Infection, Corynebacterium Diphtheriae Infection

Reviewed By:
Timothy Yarboro, M.D.
Rafiu Ariganjoye, M.D., MBA, FAAP


Diphtheria is a highly contagious, acute bacterial infection. It was once a leading cause of death among children. Widespread use of the diphtheria vaccine has made it extremely rare in areas of the developed western world where most people are immunized against the disease.

Diphtheria occurs when a person comes into contact with the airborne bacteria that cause the disease. These bacteria attach to a person’s skin or the mucous membranes lining the nose and throat.

When diphtheria occurs in the respiratory system, it produces symptoms that may appear similar to a common cold, such as a sore throat, cough and swollen neck glands. The characteristic feature of diphtheria is the growth of a thick, leather-like material on mucous membranes. It can be sticky or fuzzy and is gray, brown, black or white in color. This material also appears when diphtheria occurs in a wound on the skin.

Complications of diphtheria include airway obstruction and respiratory failure in young children. Infection can also spread to other organs of the body, including the heart, kidneys and central nervous system.

Parents who suspect their child (or anyone in the household) may have diphtheria should contact their child’s physician immediately. A physical examination that includes a throat culture (or swab from the site of infection) can confirm a diagnosis of diphtheria. If one member of a household has diphtheria, other household members may need to be tested to see if the disease has spread. In addition, other household members may be treated with antibiotics, even without evidence of having contracted the disease.

Treatment for severe cases of diphtheria is usually provided in a hospital. Patients may be confined to prevent spread of the disease among people who have not been immunized against it. Antitoxin and antibiotic medications are both provided. Diphtheria vaccines are also administered, since contracting diphtheria does not provide immunity to the disease. Patients typically remain in the hospital for two to six weeks, or until fully recovered.  

Diphtheria is preventable with immunization. A schedule has been recommended by the U.S. Centers for Disease Control and Prevention(CDC), American Academy of Pediatrics (AAP) and American Academy of Family Physicians (AAFP). This involves a primary series of vaccines that are given at staggered time intervals – three shots are delivered during infancy and two shots are administered during childhood. The remaining booster shots are given during adolescence and continue throughout adulthood.

People who do not receive all the necessary shots are at increased risk of contracting diphtheria. Maintaining up-to-date immunization throughout one’s life is an important component of preventing diphtheria. This is especially important when traveling to countries where diphtheria outbreaks occur (e.g., central Asia, Africa), or when in close contact with immigrants from these countries. It is also important when living in crowded or unclean environments. There are steps parents can take to alleviate the discomfort of vaccination for their infant or child. Serious adverse effects of the vaccine are rare, although there are signs to look for that may indicate an allergic reaction or particular vulnerability to side effects of the vaccine.

About diphtheria

Diphtheria is a disease that has been practically eliminated in the United States with immunizations. Prior to widespread use of vaccines developed to prevent diphtheria, the disease was a leading cause of death for children and was once called the “strangling angel of children.” In 1921, there were over 200,000 cases of diphtheria and more than 15,000 deaths, according to the U.S. Centers for Disease Control and Prevention(CDC). Today, diphtheria occurs rarely because most people are immunized against the disease.

Diphtheria is a contagious bacterial infection that affects human mucous membranes and skin. A person becomes infected by inhaling airborne bacteria released when an infected person coughs, sneezes or laughs. It can also occur from direct contact with the bacteria from contaminated surfaces (e.g., beverage containers, doorknobs) or secretions from infected skin sores.  

It may be difficult to know when a person comes into contact with someone with the disease. A person with diphtheria may be contagious for as long as two to six weeks after infection – even if they display no symptoms of the disease. Some people carry the bacteria but never develop symptoms, although they may infect others. The incubation period of diphtheria is two to five days. Humans are the only known reservoir of the toxin-producing bacterium that causes diphtheria.  

After entering the body, the bacteria remain in the upper layers of skin and mucous lining of the nose and throat. The bacteria multiply and may cause inflammation. Most forms of the bacterium produce a toxin that attacks and kills local tissue. A collection of dead tissue, protein, bacteria and other cells congregate – creating a thick, fuzzy/sticky and leather-like material at the site of infection. This distinguishing feature of the disease is noted in the name of the bacterium that causes diphtheria: Corynebacterium diphtheriae (or C. diphtheriae), which means “leather hide” in Greek.  In some cases, diphtheria skin infection may resemble impetigo, another skin infection. Physicians may need to distinguish between these infections to determine the proper course of treatment.

Most cases of diphtheria involve the upper respiratory system, primarily affecting the nose and throat. When diphtheria occurs in these areas, it can cause a sore throat and swollen neck glands. Breathing difficulties may also occur, which can cause airway obstruction and respiratory failure in young children. Diphtheria may also occur in the skin, producing open wounds that do not heal – also with the characteristic thick, sticky material in the area. The eyes, ears and genitals may also be affected, but this is rare. In severe cases of diphtheria, toxin can spread via the bloodstream to other areas of the body, such as the heart and kidneys. Myocarditis (inflammation of the heart muscle) is a common complication of the disease. Diphtheria can also lead to nerve damage and paralysis. It is estimated that half the people who are infected with diphtheria and who do not receive treatment for it may die.

Types and differences of diphtheria

Diphtheria can affect different parts of the body. The bacteria that cause diphtheria stick to the mucous membranes of the nose and throat, as well as open wounds in the skin. The two main types of diphtheria are based on the site of infection:

  • Respiratory diphtheria. Among nonimmunized people, diphtheria primarily infects the respiratory system. The most common areas of infection are the tonsils and pharynx (throat), followed by the nose and larynx (voice box). Infection in these areas can lead to life-threatening airway obstruction, especially for young children. The toxins released by diphtheria bacteria can also travel through the bloodstream and affect the heart, kidneys and central nervous system.
  • Cutaneous diphtheria. Occurs when diphtheria bacteria enter the body through a wound in the skin. This may include the site of a puncture, burn, bite or other type of injury. It is less common than respiratory diphtheria and is rarely associated with complications that affect other areas of the body.

Diphtheria may also occur at other body locations, such as the eyes, ears and genitals (internal and external). Although bacteria can enter the body at these locations, it is less common than either respiratory or cutaneous diphtheria.

Infant issues for diphtheria

Signs of diphtheria that are most common in infants include sores in the nostrils and upper lip. Infants should be vaccinated for diphtheria beginning as early as two months of age. In order to be immunized against diphtheria, infants are given a series of DTaP (diphtheria and tetanus toxoids and acellular pertussis) shots. Each shot includes vaccines for diphtheria, tetanus and pertussis (whooping cough). The DTaP shots are safe and effective vaccines for infants.

During the first year of life, an infant is given a total of three DTaP shots – usually at the ages of two months, four months and six months old.

Infants who receive the shots may experience some discomfort. Parents may comfort their child by holding the infant in their arms while they receive the shot (as long as the physician allows this). Parents may also wish to bring along the baby’s favorite toy or blanket.

To relieve any pain felt in the area of the injection, a physician may apply pressure or vibrate the skin near the injection site immediately after the injection. This can help reduce the perception of pain, since the pressure or vibration competes with the sensation of pain for the baby’s attention. The physician may also recommend applying a painkilling cream on the skin one hour before the shot.

After the shot, parents may apply a warm washcloth to the injection site to soothe any discomfort. Acetaminophen provided before the shot or immediately afterward may help reduce an infant’s discomfort. However, parents should consult with the pediatrician prior to giving their infant any medications, including over-the-counter drugs such as acetaminophen. Moving the limb where the injection was received may also help reduce soreness in the area.

If an infant has a fever on the day he or she is scheduled to receive a vaccine, parents should consult with the pediatrician about whether to reschedule the shot. The possible side effects of the vaccine (e.g., soreness, drowsiness, irritability) may worsen symptoms of an already sick child. In addition, parents may be unable to distinguish a potential adverse reaction to the shot from signs of an existing illness.

Parents should immediately consult a physician if they notice any of the following signs after their infant receives a diphtheria vaccine:

  • Persistent crying for three hours at a time within two days of shot

  • Fever (at least 105 degrees Fahrenheit/40.5 degrees Celsius) within two days of shot

  • Allergic reaction (e.g., swelling of the mouth, throat, face)

  • Seizures within three to seven days of shot

  • Breathing difficulty

  • Shock or collapse within two days of shot

Childhood issues for diphtheria

By the time children are six years old, they should have received a total of five doses of the diphtheria vaccine. Three shots are given during infancy. After infancy, a child will receive the fourth shot between the ages of 15 and 18 months, and the fifth between the ages of four and six years old. Getting this complete childhood series of vaccines is an important first step toward a person’s lifelong immunization against diphtheria. Booster shots are given thereafter.

Receiving injections can be a frightening and upsetting experience for children. Parents can help reduce this fear or anxiety in their children in the following ways:

  • Explain what will happen and how the shot keeps the child healthy
  • Advise the child to be brave, but that crying is okay
  • Distract the child (e.g., counting, singing, looking away) at moment of injection
  • Remain calm so the child does not pick up any anxiety
  • Praise the child after the injection
  • Plan fun activities afterward so the overall experience is pleasant

Parents should immediately consult a physician if they notice any of the following signs after their child receives a diphtheria vaccine:

  • Persistent crying for three hours at a time within two days of shot
  • Fever (at least 105 degrees Fahrenheit/40.5 degrees Celsius) within two days of shot
  • Allergic reaction (e.g., swelling of the mouth, throat, face)
  • Seizures within three to seven days of shot
  • Breathing difficulty
  • Shock or collapse within two days of shot

Adolescent and adult issues for diphtheria

Booster shots are recommended every 10 years for adolescents and adults. After receiving vaccines for diphtheria in childhood, many adolescents and adults fail to receive their booster shots. These additional vaccines are necessary for continued immunization against diphtheria. Parents of adolescents are encouraged to make sure that their children are up-to-date on immunizations.

Patients who may be pregnant can safely receive the diphtheria booster shot. A pregnant patient may also begin diphtheria immunizations (if she has not previously received the DTaP series) while pregnant. Pregnant patients should receive the Td (tetanus and diphtheria toxoid) version of the vaccine if never previously immunized, or if the last diphtheria shot was at least 10 years prior.  Vaccination of a pregnant patient may also provide some immunity to the fetus in the womb. Fetuses receive some antibodies that are passed through the placenta. Once born, babies can also receive antibodies via breastfeeding. These antibodies may provide some level of protection against disease, including diphtheria, until infants are old enough to receive vaccines themselves.

Risk factors and causes of diphtheria

In order to contract diphtheria, a person must first come into contact with the bacteria that cause the disease. This generally happens when particles made airborne by the coughing or sneezing of a person infected with diphtheria are inhaled. It may also occur by contact with contaminated surfaces, or contact with secretions from an infected wound of a person with diphtheria.

The following factors may increase a person’s risk of contracting diphtheria:

  • Immunity status. Children or adults without up-to-date diphtheria immunizations face the highest risk of contracting the disease. This includes children who have never been vaccinated or did not receive the entire series of shots. It may also include adults who were vaccinated as children, but have not received booster shots every 10 years to maintain their immunity throughout adulthood.

  • Age. Children under five years old and adults over 60 years old have underdeveloped or underperforming immune systems, leading to an increased risk of contracting diphtheria.

  • Crowded, unclean conditions. Unsanitary environments and those that are crowded with people make it easy to catch and spread bacterial infections such as diphtheria. This includes situations in which people live on the street (e.g., the homeless) or are confined to shelters following a natural disaster.

  • Social and economic status. Poverty and low social standing may limit access to vaccines or result in reduced levels of education about the importance of diphtheria immunizations. In addition, lower rates of immunization among these groups result in an increased risk of contracting diphtheria. Poverty and socioeconomic factors can affect nourishment levels. Being undernourished can reduce the immune system response, increasing the risk of infection. High rates of diphtheria have been identified among American Indian populations in the late 20th century – although this may be more related to the social and economic factors American Indians face rather than race or ethnicity.

  • Season. Although diphtheria can occur year-round, it occurs more often during the fall and winter months among nonimmunized populations.

  • Compromised immune systems. People with immune system deficiencies may be unable to fight off infection, increasing their risk of contracting diphtheria.

  • Travel to countries with no or inadequate immunization. Traveling to areas of the world where diphtheria outbreaks occur (e.g., Africa, Central Asia) can place people who are not current on their immunizations at risk of contracting diphtheria.

  • Contact with immigrants from countries with no or inadequate immunization. People who do not have up-to-date immunizations against diphtheria are at increased risk of contracting the disease if they come into contact with immigrants from countries where diphtheria outbreaks occur.

Signs and symptoms of diphtheria

Parents should immediately contact a physician if they believe their child (or anyone in the household) may have diphtheria.

Signs and symptoms of the disease usually appear within two to four days of infection, although it may take as many as 10 days for symptoms to show. Early signs of respiratory diphtheria may resemble those of a cold (e.g., a sore throat, nasal discharge, discomfort, pain when swallowing and swollen neck glands). Patients may experience low-grade fever, although fever is rare. Additional signs to look for include:

  • Thick, discolored coating of the throat. A lining of noticeably gray, brown, black or white material that may occur within the nose, throat or airway. It is usually thick and leather-like. It may be most obvious when looking at the back of the throat via a child’s open mouth. This leather-like coating is what distinguishes diphtheria from other infections that may cause a sore throat (e.g., strep throat). Bleeding usually results when attempting to remove this coating. This lining usually forms within two to three days after symptoms begin.

  • Bull-neck appearance. When the muscles and bones of the lower half of the face (e.g., chin, jaw, collarbone) seem to disappear into the flesh of the neck. This is due to extreme swelling of the neck area caused by diphtheria. Children with bull-neck appearance may tilt their heads back to relieve pressure on the throat.

  • Breathing difficulty. This may occur when the airway becomes blocked due to swelling and/or the buildup of material on the lining of the nose, throat and airway. This can be life-threatening to young children who have smaller-sized airways that can be more easily blocked, restricting breathing.

  • Coughing. This may occur in an attempt to clear airways that have been restricted due to the buildup of material lining the respiratory track.

  • Signs of shock. These may include rapid heartbeat, low blood pressure, sweating, pale and cold skin, and an anxious appearance.

When diphtheria affects a person’s skin, the following signs may occur at the site of infection:

  • Nonhealing open wound with sharply defined borders
  • Rash with flaking skin
  • Fluid discharge
  • Pain, tenderness
  • Redness
  • Swelling
  • Growth of thick, sticky or fuzzy material that is gray, brown, black or white

Diagnosis methods for diphtheria

Parents who suspect diphtheria in their child (or anyone in their household) should contact a physician immediately.

A medical history and physical examination will likely take place. Parents should provide a description of their child’s symptoms, including symptom duration and severity.

A physician may perform a throat culture to diagnose diphtheria. This is a painless procedure in which a long cotton swab is used to remove a small tissue sample from the patient’s throat. In some cases, a sample may be taken from the patient’s nose or site of infection if diphtheria is suspected in an open sore on other areas of the body. The sample is then analyzed under a microscope to identify the bacteria that cause diphtheria.

If the sample is positive (indicating the presence of diphtheria), other household members may need to see a physician for an examination as well. This can determine whether the disease has spread throughout the household.

Throat cultures or samples from the site of infection are again taken and analyzed after a patient has undergone treatment for diphtheria to ensure that the disease has been effectively treated. Physicians are required to notify local health departments about confirmed cases of respiratory diphtheria. These agencies report to the U.S.Centers for Disease Control and Prevention (CDC)for tracking. In addition, efforts may be made to identify and treat other infected people, as well as locate the source of infection. Since 1980, non-respiratory cases of diphtheria (e.g., diphtheria that affects the skin) do not need to be reported.

Treatment options for diphtheria

Most children and adults with diphtheria will need to be treated in a hospital. The earlier treatment is administered, the better. As the disease progresses, toxins may be released into the bloodstream, causing extensive or life-threatening organ damage. However, most people with diphtheria survive the disease as well as its complications.

Because diphtheria can be easily spread to those who are not immunized against it, patients hospitalized for the disease may be isolated from others who may be considered at increased risk for diphtheria (e.g., people not immunized, young children, older adults).

For patients with diphtheria that affects the skin, the infection site will be thoroughly cleaned with soap and water. For patients with respiratory diphtheria, a physician may remove some of the thick membrane lining from the throat if it is causing breathing difficulties.

The usual course of treatment for diphtheria includes all three of the following:

  • Antitoxins. Medication designed to chemically neutralize the bacteria in the body, disabling and rendering the toxin ineffective. Equine antitoxins, made from horses, are usually provided in a single dose intravenously (into a vein). However, tests for sensitivity to horse serum should be performed on the patient prior to the use of this medication.

  • Antibiotics. Drugs necessary to kill the bacteria that cause diphtheria. This helps to clear the infection and reduce the length of time a person may be contagious. Patients being treated for diphtheria may receive antibiotics for up to two weeks. The patient is tested to ensure the infection has been eliminated before treatment is stopped, by documenting two consecutive negative cultures. Antibiotic therapy is however, not a substitute for antitoxin.

  • Immunization. After successful treatment for diphtheria, patients are given vaccines to prevent diphtheria in the future. Immunization is necessary because contracting diphtheria does not protect a person from getting it again in the future. 

Patients being treated for diphtheria may need to remain in the hospital for two to six weeks of bed rest, or until fully recovered. This is especially important if the diphtheria toxin has affected the heart.

Household members of the patient may also require treatment. This usually consists of antibiotics and a booster shot of the diphtheria vaccine. A physician may decide to administer these treatments even before receiving evidence that confirms diphtheria.   

Some people may carry the bacteria that cause diphtheria in their bodies, yet never develop an infection or show symptoms. These people are known as carriers. If identified, they are typically isolated (or quarantined) and treated with antibiotics until tests for infection return negative. Carriers are then normally vaccinated for the disease. Improperly immunized people may be exposed and become carriers.

Advanced cases of diphtheria may require the following additional treatment, also administered in a hospital:

  • Ventilator. A machine that helps a patient breathe. This may be used in cases of severe airway obstruction.

  • Intravenous (I.V.) fluids, nutrition. Fluids and liquid nutrition that are administered via a needle into a vein. This may be necessary in cases of severe difficulty swallowing, to avoid dehydration and malnutrition during recovery.

  • Other medications. Additional drugs may be necessary to treat other areas of the body that have been affected by the spread of the diphtheria toxin (e.g., heart, kidneys, central nervous system).

Prevention methods for diphtheria

Diphtheria is a preventable disease. Immunization has nearly eliminated incidence of the disease in the United States. However, diphtheria remains a problem in certain areas of the world (e.g., Central Asia, Africa) with no or inadequate immunization programs. Without continued immunization in the United States, the disease could return and spread.

Immunization against diphtheria combines the vaccines for several conditions into a single shot. This shot is available in the following age-specific formulations:

  • DTaP (diphtheria and tetanus toxoids and acellular pertussis). Protects against diphtheria, tetanus and pertussis (whooping cough). The DTaP shot is provided to infants and children up to age seven. This shot is not recommended for children seven years or older as it may increase the risk of side effects after vaccination. This shot is less likely to cause side effects than an earlier version called DTP.

  • DT(diphtheria and tetanus toxoids). This shot protects against diphtheria and tetanus, but does not include the vaccine for pertussis. A component of the pertussis vaccine may sometimes cause complications in people with certain existing conditions (e.g., seizure disorder, allergies). This shot is used for infants and children who cannot receive the DTaP shot.

  • Tdap (tetanus and diphtheria toxoids and acellular pertussis). Protects against the same conditions as the DTaP, but with a lower concentration level of vaccine (because less immune protection is needed after a person has received the DTaP shots). This shot is given as a booster to adolescents age 11 to 18 years old.

  • Td (tetanus and diphtheria toxoids). Protects against diphtheria and tetanus only – it does not contain the vaccine for pertussis. The Td shot features even lower concentration levels than the Tdap. It may be provided to adolescents and adults and is recommended every 10 years as a booster shot.   

In order to achieve proper immunization against diphtheria, children must receive a series of shots within certain time periods. The U.S. Centers for Disease Control and Prevention (CDC), American Academy of Pediatrics (AAP) and American Academy of Family Physicians (AAFP) have recommended the following diphtheria immunization schedule:

Shot #AgeExceptionsType
Dose 1Infants age two monthsMay be given as early as six weeksDTaP
Dose 2Infants age four monthsIf behind schedule, second dose can be given at least four weeks after previous shotDTaP
Dose 3Infants age six monthsIf behind schedule, third dose can be given at least four weeks after previous shotDTaP
Dose 4Children age 15 months to 18 monthsMay be given as early as 12 months of age, as long as previous shot was given at least six months prior.DTaP
Dose 5Children age four years to six yearsMay be given earlier, as long as previous shot was given at least six months prior. If the previous shot was not administered until after age four, this dose is not necessary.DTaP
BoosterAdolescents age 11 years to 12 yearsMay be given up to age 18. Must be at least five years after previous shot.Tdap
BoosterAdults (every 10 years thereafter) Td

When vaccinated as recommended, children should have received a total of five shots by the time they are six years old. Adults should continue to receive booster doses every 10 years for the rest of their lives. Without up-to-date vaccinations, people who were vaccinated in childhood may still contract the disease as an adult.

Children between the ages of seven years and 18 years who have not received any or all of the required vaccines can catch up on their immunizations with the following schedule:

  • Dose 1

  • Dose 2 (four to eight weeks later)

  • Dose 3 (six to 12 months later)

  • Dose 4 (six months later – if first vaccine provided when less than a year old, and the child is currently under 11 years old); or

  • Dose 4 (five years later – if first vaccine provided when child was 12 months or older)

The vaccines are safe and effective in children and adults. The Food and Drug Administration (FDA) tests and approves all recommended vaccines.

Side effects may occur and can include soreness or redness at the injection site, drowsiness, low-grade fever and irritability the day after injection. An allergic reaction to the vaccine is rare. In extremely rare cases, neurological damage and/or seizures have occurred in children who received the DTaP vaccine. This finding is controversial, however, since a causal connection between the vaccine and these effects has not been proven.  

Receiving the vaccine when a person has a moderate or severe illness (e.g., fever) may worsen existing symptoms. In addition, people with certain conditions may be at risk for complications if they receive certain types of the vaccine. Patients or their parents should consult a physician about the timing of vaccination and which type of vaccine may be appropriate if any of the following are present:

  • Current moderate to severe illness
  • Seizure disorder
  • Neurological disease
  • Allergic reaction to previous vaccines
  • Pregnancy

Because diphtheria is a contagious bacterial disease, practicing good hygiene can help prevent the spread of infection among people who are not immunized against diphtheria. This can include covering the mouth and nose when coughing or sneezing, promptly throwing away used tissues, and frequent hand washing (especially before and after contact with the eyes and mouth). 

Questions for your doctor regarding diphtheria

Preparing questions in advance can help patients and parents have more meaningful discussions with physicians regarding their or their child’s treatment options. The following questions related to diphtheria may be helpful:

  1. My child has a sore throat and the area at the back of his/her mouth doesn’t look normal. Could this be diphtheria?

  2. My child has an open sore on his/her leg. A sticky, gray-colored matter has grown in the area. Could this be diphtheria?

  3. If I suspect diphtheria, should I take my child to an emergency room or clinic, or come into your office?

  4. If one child has diphtheria, what are the chances my other children will catch it?

  5. How long will my child need to be hospitalized if he/she has diphtheria?

  6. Will other household members need to be tested or treated if one of us has diphtheria?

  7. When should my child begin his/her immunizations for diphtheria?

  8. Which type of vaccine is recommended for my child?

  9. If diphtheria rarely occurs, why is my child receiving a vaccine for it?

  10. Is it dangerous for my child to receive several different immunizations at the same time?

  11. Does the diphtheria vaccine contain the preservative thimerosal?

  12. What side effects of the diphtheria vaccine is my child likely to get?

  13. After receiving the vaccine, what changes in my child’s condition should I tell you about?

  14. My child has not received all the diphtheria shots required – is it too late? How would you recommend we catch up to get back on schedule?
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