Encyclopedia / D / Diphtheria



Diphtheria is a life-threatening disorder caused by a highly contagious bacterial infection caused by the bacterium Corynebacterium diphtheriae.


Diphtheria is especially dangerous when it affects the throat, where it can produce a thick gray membrane that may grow large enough to obstruct breathing. The most serious complications are caused by a toxin produced by the diphtheria bacterium that can damage the heart, nervous system and, less often, the kidneys.

Diphtheria most often strikes before the age of 15 and is fatal in nearly 10 percent of cases. Recovery tends to be slow in those who do survive.

Due to widespread immunization efforts, the disease is now extremely rare in developed countries. In modernized countries the most common infection with the diphtheria bacterium involves the skin and is rarely associated with systemic manifestations.


The bacteria live in an infected person's nose, throat, skin, or eye discharges, and are passed to others in close contact through coughing or sneezing. You can also catch diphtheria from touching the open sores on someone with skin diphtheria, a condition that occurs in tropical countries and in any area with crowded conditions and inadequate hygiene. Skin diphtheria causes a rash that is hard to distinguish from impetigo.

Very rarely, food contaminated with the diphtheria bacterium can infect others. Diphtheria outbreaks have occurred recently in the former Soviet Union.


Diphtheria toxin usually attacks the tonsils first and causes fever, red sore throat, weakness, and headache. The toxin destroys the normal throat tissue, causing the throat to swell. As the tissue dies, the toxin forms a thick, grayish white membrane that completely covers the throat. The appearance of this membrane is important in making a diagnosis. Without treatment, the membrane will spread to cover the entire throat and larynx.

The victim has difficulty breathing and cannot talk. The lymph glands in the neck become enlarged and swollen. The breath has an unpleasant, distinct odor. Skin diphtheria causes a nasal discharge and excoriated skin around the nose.


If a diagnosis of diphtheria is suspected upon physical examination, diphtheria antitoxin is administered (either intravenously or by intramuscular injection) before laboratory results of the culture confirm the diagnosis. The antitoxin helps to prevent damage caused by the bacterial toxin to vital organs. Antibiotics are give to treat the infection.

Hospitalization is usually required, as intravenous fluids, supplementary oxygen, bed rest, and careful monitoring of heart function are often warranted.

If the membrane in the back of the throat obstructs breathing, a tube may be passed through the mouth or nose; in very serious cases, a tracheostomy (insertion of a breathing tube through a surgical opening in the throat) may be needed.

Treatment for congestive heart failure may also be required.


Is diphtheria still a problem?

Are there risks to the immunization?

After vaccination is a booster shot necessary?

If we travel, should we take precautions against diphtheria?

Immunization for diphtheria has been part of routine well-child care for decades. This is the "D" in the "DPT" shots. Immunization of all infants and booster doses throughout life will prevent any resurgence of diphtheria.

Diphtheria vaccine is made of a toxoid, which is a weakened form of the diphtheria toxin. This stimulates the immune system to make antibodies against the toxin to protect against the disease. The immunity wanes so that a booster is needed every ten years.

The toxoid comes in two strengths - children younger than seven need the higher concentration to develop immunity. Anyone older than seven should get the low concentration because it has fewer side effects and is strong enough to boost immunity.

The vaccine labeled with a capital D is the strong concentration, and a lower case d stands for the lower concentration toxoid.