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Diphtheria is a potentially fatal, contagious disease that usually involves the nose, throat, and air passages, but may also infect the skin. Its most striking feature is the formation of a grayish membrane covering the tonsils and upper part of the throat.


Like many other upper respiratory diseases, diphtheria is most likely to break out during the winter months. At one time it was a major childhood killer, but it is now rare in developed countries because of widespread immunization. Since 1988, all confirmed cases in the United States have involved visitors or immigrants. In countries that do not have routine immunization against this infection, the mortality rate varies from 1.5-25%.
Persons who have not been immunized may get diphtheria at any age. The disease is spread most often by droplets from the coughing or sneezing of an infected person or carrier. The incubation period is two to seven days, with an average of three days. It is vital to seek medical help at once when diphtheria is suspected, because treatment requires emergency measures for adults as well as children.

Causes and symptoms

The symptoms of diphtheria are caused by toxins produced by the diphtheria bacillus, Corynebacterium diphtheriae (from the Greek for "rubber membrane"). In fact, toxin production is related to infections of the bacillus itself with a particular bacteria virus called a phage (from bacteriophage; a virus that infects bacteria). The intoxication destroys healthy tissue in the upper area of the throat around the tonsils, or in open wounds in the skin. Fluid from the dying cells then coagulates to form the telltale gray or grayish green membrane. Inside the membrane, the bacteria produce an exotoxin, which is a poisonous secretion that causes the life-threatening symptoms of diphtheria. The exotoxin is carried throughout the body in the bloodstream, destroying healthy tissue in other parts of the body.
The most serious complications caused by the exotoxin are inflammations of the heart muscle (myocarditis) and damage to the nervous system. The risk of serious complications is increased as the time between onset of symptoms and the administration of antitoxin increases, and as the size of the membrane formed increases. The myocarditis may cause disturbances in the heart rhythm and may culminate in heart failure. The symptoms of nervous system involvement can include seeing double (diplopia), painful or difficult swallowing, and slurred speech or loss of voice, which are all indications of the exotoxin's effect on nerve functions. The exotoxin may also cause severe swelling in the neck ("bull neck").
The signs and symptoms of diphtheria vary according to the location of the infection:


Nasal diphtheria produces few symptoms other than a watery or bloody discharge. On examination, there may be a small visible membrane in the nasal passages. Nasal infection rarely causes complications by itself, but it is a public health problem because it spreads the disease more rapidly than other forms of diphtheria.


Pharyngeal diphtheria gets its name from the pharynx, which is the part of the upper throat that connects the mouth and nasal passages with the voice box. This is the most common form of diphtheria, causing the characteristic throat membrane. The membrane often bleeds if it is scraped or cut. It is important not to try to remove the membrane because the trauma may increase the body's absorption of the exotoxin. Other signs and symptoms of pharyngeal diphtheria include mild sore throat, fever of 101-102°F (38.3-38.9°C), a rapid pulse, and general body weakness.


Laryngeal diphtheria, which involves the voice box or larynx, is the form most likely to produce serious complications. The fever is usually higher in this form of diphtheria (103-104°F or 39.4-40°C) and the patient is very weak. Patients may have a severe cough, have difficulty breathing, or lose their voice completely. The development of a "bull neck" indicates a high level of exotoxin in the bloodstream. Obstruction of the airway may result in respiratory compromise and death.


This form of diphtheria, which is sometimes called cutaneous diphtheria, accounts for about 33% of diphtheria cases. It is found chiefly among people with poor hygiene. Any break in the skin can become infected with diphtheria. The infected tissue develops an ulcerated area and a diphtheria membrane may form over the wound but is not always present. The wound or ulcer is slow to heal and may be numb or insensitive when touched.


Because diphtheria must be treated as quickly as possible, doctors usually make the diagnosis on the basis of the visible symptoms without waiting for test results.
In making the diagnosis, the doctor examines the patient's eyes, ears, nose, and throat in order to rule out other diseases that may cause fever and sore throat, such as infectious mononucleosis, a sinus infection, or strep throat. The most important single symptom that suggests diphtheria is the membrane. When a patient develops skin infections during an outbreak of diphtheria, the doctor will consider the possibility of cutaneous diphtheria and take a smear to confirm the diagnosis.

Laboratory tests

The diagnosis of diphtheria can be confirmed by the results of a culture obtained from the infected area. Material from the swab is put on a microscope slide and stained using a procedure called Gram's stain. The diphtheria bacillus is called Gram-positive because it holds the dye after the slide is rinsed with alcohol. Under the microscope, diphtheria bacilli look like beaded rod-shaped cells, grouped in patterns that resemble Chinese characters. Another laboratory test involves growing the diphtheria bacillus on a special material called Loeffler's medium.


Diphtheria is a serious disease requiring hospital treatment in an intensive care unit if the patient has developed respiratory symptoms. Treatment includes a combination of medications and supportive care:


The most important step is prompt administration of diphtheria antitoxin, without waiting for laboratory results. The antitoxin is made from horse serum and works by neutralizing any circulating exotoxin. The doctor must first test the patient for sensitivity to animal serum. Patients who are sensitive (about 10%) must be desensitized with diluted antitoxin, since the antitoxin is the only specific substance that will counteract diphtheria exotoxin. No human antitoxin is available for the treatment of diphtheria.
The dose ranges from 20,000-100,000 units, depending on the severity and length of time of symptoms occurring before treatment. Diphtheria antitoxin is usually given intravenously.


Antibiotics are given to wipe out the bacteria, to prevent the spread of the disease, and to protect the patient from developing pneumonia. They are not a substitute for treatment with antitoxin. Both adults and children may be given penicillin, ampicillin, or erythromycin. Erythromycin appears to be more effective than penicillin in treating people who are carriers because of better penetration into the infected area.
Cutaneous diphtheria is usually treated by cleansing the wound thoroughly with soap and water, and giving the patient antibiotics for 10 days.

Supportive care

Diphtheria patients need bed rest with intensive nursing care, including extra fluids, oxygenation, and monitoring for possible heart problems, airway blockage, or involvement of the nervous system. Patients with laryngeal diphtheria are kept in a croup tent or high-humidity environment; they may also need throat suctioning or emergency surgery if their airway is blocked.
Patients recovering from diphtheria should rest at home for a minimum of two to three weeks, especially if they have heart complications. In addition, patients should be immunized against diphtheria after recovery, because having the disease does not always induce antitoxin formation and protect them from reinfection.

Prevention of complications

Diphtheria patients who develop myocarditis may be treated with oxygen and with medications to prevent irregular heart rhythms. An artificial pacemaker may be needed. Patients with difficulty swallowing can be fed through a tube inserted into the stomach through the nose. Patients who cannot breathe are usually put on mechanical respirators.


The prognosis depends on the size and location of the membrane and on early treatment with antitoxin; the longer the delay, the higher the death rate. The most vulnerable patients are children under age 15 and those who develop pneumonia or myocarditis. Nasal and cutaneous diphtheria are rarely fatal.


Prevention of diphtheria has four aspects:


Universal immunization is the most effective means of preventing diphtheria. The standard course of immunization for healthy children is three doses of DPT (diphtheria-tetanus-pertussis) preparation given between two months and six months of age, with booster doses given at 18 months and at entry into school. Adults should be immunized at 10 year intervals with Td (tetanus-diphtheria) toxoid. A toxoid is a bacterial toxin that is treated to make it harmless but still can induce immunity to the disease.

Isolation of patients

Diphtheria patients must be isolated for one to seven days or until two successive cultures show that they are no longer contagious. Children placed in isolation are usually assigned a primary nurse for emotional support.

Identification and treatment of contacts

Because diphtheria is highly contagious and has a short incubation period, family members and other contacts of diphtheria patients must be watched for symptoms and tested to see if they are carriers. They are usually given antibiotics for seven days and a booster shot of diphtheria/tetanus toxoid.

Reporting cases to public health authorities

Reporting is necessary to track potential epidemics, to help doctors identify the specific strain of diphtheria, and to see if resistance to penicillin or erythromycin has developed.



Chambers, Henry F. "Infectious Diseases: Bacterial & Chlamydial." In Current Medical Diagnosis and Treatment, 1998, edited by Stephen McPhee, et al., 37th ed. Stamford: Appleton & Lange, 1997.

Key terms

Antitoxin — An antibody against an exotoxin, usually derived from horse serum.
Bacillus — A rod-shaped bacterium, such as the diphtheria bacterium.
Carrier — A person who may harbor an organism without symptoms and may transmit it to others.
Cutaneous — Located in the skin.
Diphtheria-tetanus-pertussis (DTP) — The standard preparation used to immunize children against diphtheria, tetanus, and whooping cough. A so-called "acellular pertussis" vaccine (aP) is usually used since its release in the mid-1990s.
Exotoxin — A poisonous secretion produced by bacilli which is carried in the bloodstream to other parts of the body.
Gram's stain — A dye staining technique used in laboratory tests to determine the presence and type of bacteria.
Loeffler's medium — A special substance used to grow diphtheria bacilli to confirm the diagnosis.
Myocarditis — Inflammation of the heart tissue.
Toxoid — A preparation made from inactivated exotoxin, used in immunization.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


an acute, highly contagious childhood disease that generally affects the membranes of the throat and, less frequently, the nose; in rare instances it can affect other parts of the body, notably the skin, following an open wound. Caused by the bacillus Corynebacterium diphtheriae, it can be fatal if not treated promptly. However, repeated exposure to the causative organisms may provide a natural immunity. adj., adj diphthe´rial, diphther´ic, diphtherit´ic.

Diphtheria spreads in droplets of moisture from the mouth, nose, or throat of an infected person. It may also be spread by handkerchiefs, towels, eating utensils, or any other object used by an infected person or sprayed by his coughing or sneezing. It may also be transmitted by a healthy person who is nevertheless a carrier of the disease or by someone who is convalescing from diphtheria. The incubation period of the disease is generally between 2 and 5 days, sometimes longer. An infected person may continue to have the bacilli in his throat from 2 to 4 weeks after he has recovered from its effects.
Symptoms. The first symptoms of diphtheria usually include sore throat, fever, headache, and nausea. Patches of grayish or dirty-yellowish membrane form in the throat, and gradually grow into one membrane. This membrane, combined with swelling of the throat, may interfere with swallowing or breathing. In severe cases, when other measures fail, a tracheostomy may be necessary to restore breathing.

The diphtheria bacillus also produces a toxin that spreads throughout the body and may damage the heart and nerves permanently. Diagnosis of the disease can be verified by identifying the causative organisms from throat cultures. Susceptibility to diphtheria is determined by the Schick test. A positive skin test indicates the absence of circulating antibodies to the diphtheria toxin, but a pseudoreaction can also occur.
Treatment. Diphtheria antitoxin is administered to counteract the toxic reaction from the bacillus. Prognosis depends on the severity of the infection and especially on how soon the antitoxin is given. Rest, antibiotics, and general hygienic measures are used to combat the infection. Oxygen is administered as necessary to relieve dyspnea and cyanosis. Cardiac complications are usually more severe in adults; thus the convalescent period is extended for these patients.
Prevention. Immunization should be begun between the sixth and eighth weeks of an infant's life. Diphtheria and tetanus toxoids and pertussis vaccine (DTaP) is the preferred vaccine for all doses in the vaccination series. Booster doses are also needed later in life. (See also table under immunization.)

Once one of the most fatal diseases of childhood, cases of diphtheria and death from the disease have become almost nonexistent in countries where mass immunization has been practiced.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


(dif-thēr'ē-ă), Avoid the misspelling/mispronunciation dipheria.
A specific infectious disease due to the bacterium Corynebacterium diphtheriae and its highly potent toxin; marked by severe inflammation that can form a membranous coating, with formation of a thick fibrinous exudate, of the mucous membrane of the pharynx, the nose, and sometimes the tracheobronchial tree; the toxin produces degeneration in peripheral nerves, heart muscle, and other tissues, diphtheria had a high fatality rate, especially in children, but is now rare because of an effective vaccine.
[G. diphthera, leather]
Farlex Partner Medical Dictionary © Farlex 2012


(dĭf-thîr′ē-ə, dĭp-)
An acute infectious disease caused by the bacterium Corynebacterium diphtheriae, which infects mucous membranes of the throat, causing formation of a thick layer called the false membrane that can obstruct breathing, and producing a potent toxin that enters the bloodstream and causes systemic effects that include damage to the heart and nervous system.

diph′the·rit′ic (-thə-rĭt′ĭk), diph·ther′ic (-thĕr′ĭk), diph·the′ri·al adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Diphtheritis Infectious disease An acute, potentially fatal infection, primarily of the upper respiratory tract, throat. See DTP–Diphtheria-Tetanus-Pertussis and DTaP–acellular Pertussis vaccines.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


A specific infectious disease due to Corynebacterium diphtheriae and its highly potent toxin; marked by severe inflammation with formation of a thick membranous coating of the pharynx, the nose, and sometimes the tracheobronchial tree; the toxin produces degeneration in peripheral nerves, heart muscle, and other tissues. Symptoms include fever, fatigue, sore throat, difficulty in swallowing, and nausea. Adult morbidity ranges from 5-10%; in children younger than 5 years of age, mortality approaches 20%.
[G. diphthera, leather]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A serious, and highly infectious, disease caused by the toxin of an organism Corynebacterium diphtheriae . This normally attacks the throat causing a membrane-like exudate of clotted serum, white cells, bacteria and dead surface tissue cells to form. This may obstruct the upper air passages, necessitating an emergency artificial opening into the windpipe (a tracheostomy) to save life. The bacterial toxin can also affect the heart.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


a serious disease of the upper respiratory tract in man caused by toxins produced by the bacterium Corynebacterium diphtheriae. The toxins cause NECROSIS of epithelial cells in the throat, resulting in the production of a greyish EXUDATE that gradually forms a membrane on the tonsils and can spread upwards into the nasal passages, or downwards into the larynx causing suffocation if not treated.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005


(dif-thēr'ē-ă) Avoid the misspelling/mispronunciation dipheria.
A specific infectious disease due to infection by the bacterium Corynebacterium diphtheriae and its highly potent toxin.
[G. diphthera, leather]
Medical Dictionary for the Dental Professions © Farlex 2012

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References in periodicals archive ?
(132.) "Diphteria, Scarlet Fever", Montreal Star, 15 November 1894.

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