Questions & Answers
Diphtheria - The Disease
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  1. How common is diphtheria in the United States?

    Diphtheria was once the leading cause of death among children in the United States. Diphtheria was feared greatly. In the 1920s, 100,000-200,000 cases of diphtheria occurred each year resulting in 13,000-15,000 deaths. Diphtheria is now rare (fewer than five cases reported per year since 1980) thanks to improved living conditions and widespread immunization. However, recent surveys show that up to 60% of adults in the U.S. are not protected against diphtheria.

    Protection provided by childhood immunization decreases over time and many adults do not receive recommended booster doses (every 10 years). This is a concern because diphtheria the disease continues to occur in other parts of the world. From 1990 to 1998, more than 150,000 cases and more than 5,000 deaths were reported in the former republics of the Soviet Union. This outbreak, and others around the world, illustrates what can happen when immunity levels fall. Outbreaks in other countries also increase the risk of diphtheria importation into the United States.

  2. What causes diphtheria?
    Diphtheria is caused by a bacterium called Corynebacterium diphtheriae. The actual cause of disease is not the bacteria itself but a toxin, or poison, released into the body by the bacteria.

  3. How does diphtheria spread?
    Diphtheria bacteria live in the mouth, throat, and nose of an infected person and can be passed to others by coughing or sneezing. Occasionally, transmission occurs from skin sores or through objects soiled with discharge from sores of infected persons.

  4. How long does it take to show signs of diphtheria after being exposed?
    The incubation period is short: 2 to 5 days, with a range of 1 to 10 days.


  1. What are the symptoms of diphtheria?
    Early symptoms of diphtheria may mimic a cold with a sore throat, mild fever, and chills. Diphtheria often causes a thick coating at the back of the throat, which can make it difficult to breathe or swallow. The nose, eyes, skin, heart and kidneys are other body sites affected

  2. How serious is diphtheria?
    Diphtheria is a serious disease: 5% to 10% of people with diphtheria die. Death occurs twice as often in those (older than 40 years or younger than 5 years).


  1. What are possible complications from diphtheria?
    Most complications of diphtheria are due to diphtheria toxin. The toxin can cause swelling of the heart, leading to abnormal heart rhythms. It can also cause swelling of the nerves, which may cause temporary paralysis of some muscles. If the paralysis affects the diaphragm (the major muscle for breathing), the patient may develop pneumonia or respiratory failure. The thick membrane coating the back of the throat may cause serious breathing problems, even suffocation.

  2. How do I know if someone has diphtheria?
    The diagnosis of diphtheria can only be confirmed by laboratory testing. However, treatment is usually begun based on clinical suspicion, because early treatment improves the likelihood that a person recovers.

  3. How long is a person with diphtheria contagious?
    About 48 hours after antibiotics are started, a person is no longer contagious. However, some individuals continue to carry diphtheria bacteria even after antibiotic therapy. This is called the carrier state. Carriers should continue treatment until three consecutive laboratory tests for diphtheria are negative. People caring for a patient with diphtheria should take standard contact precautions and ensure their diphtheria immunization is up-to-date.