Diphtheria once was a major cause of illness and death among children. The United States recorded 206,000 cases of diphtheria in 1921, resulting in 15,520 deaths. Starting in the 1920s, diphtheria rates dropped quickly due to the widespread use of vaccines. Between 2004 and 2017, state health departments reported 2 cases of diphtheria in the United States. However, the disease continues to cause illness globally. In 2016, countries reported about 7,100 cases of diphtheria to the World Health Organization, but many more cases likely go unreported.

The case-fatality rate for diphtheria has changed very little during the last 50 years. The overall case-fatality rate for diphtheria is 5%–10%, with higher death rates (up to 20%) among persons younger than 5 and older than 40 years of age. Before there was treatment for diphtheria, the disease was fatal in up to half of cases.

Clinical Features

The incubation period of diphtheria is usually 2–5 days (range: 1–10 days). Diphtheria can involve almost any mucous membrane. For clinical purposes, it is convenient to classify diphtheria into a number of manifestations, depending on the site of disease:

  • Respiratory diphtheria
    • Nasal diphtheria
    • Pharyngeal and tonsillar diphtheria
    • Laryngeal diphtheria
  • Cutaneous diphtheria

Medical Management

After you make the provisional clinical diagnosis and obtain appropriate cultures, give antitoxin and antibiotics in adequate dosage to persons with suspected diphtheria and place them in isolation. You should also administer respiratory support and airway maintenance as needed.

Diphtheria Antitoxin

In the United States, clinicians can obtain diphtheria antitoxin from CDC on request. Learn more about diphtheria antitoxin and how to request it.


The recommended antibiotic treatment for diphtheria is erythromycin orally or by injection (40 mg/kg/day; maximum, 2 gm/day) for 14 days, or procaine penicillin G daily, intramuscularly (300,000 units every 12 hours for those weighing 10 kg or less, and 600,000 units every 12 hours for those weighing more than 10 kg) for 14 days. Give oral penicillin V 250 mg 4 times instead of injections to persons who can swallow. The disease is usually not contagious 48 hours after antibiotic treatment begins. However, maintain droplet and standard precautions until the patient has completed the antibiotic course and is culture-negative. Document elimination of the organism using two consecutive negative cultures after therapy is completed.

Preventive Measures

Doctor examining adult male patient

Administer a diphtheria toxoid booster, appropriate for age, to close contacts, especially household contacts if they are not up to date with diphtheria vaccination. Contacts should also receive antibiotics—a 7- to 10-day course of oral erythromycin (40 mg/kg/day for children and 1 g/day for adults). For compliance reasons, if you cannot maintain surveillance of contacts, they should receive benzathine penicillin (600,000 units for persons younger than 6 years old and 1,200,000 units for those 6 years or older). Identified carriers in the community should also receive antibiotics. Contacts should be closely monitored and antitoxin given at the first sign(s) of illness.

Treat contacts of cutaneous diphtheria as described above; however, if the strain is shown to be nontoxigenic, you can discontinue investigation of contacts.


Circulation of the bacteria appears to continue in some settings, even in populations with more than 80% childhood vaccination rates. An asymptomatic carrier state can exist even among immune individuals.

Immunity wanes over time; therefore, you should administer a booster dose of vaccine every 10 years to maintain protective antibody levels. Large populations of older adults may be susceptible to diphtheria, in both developed as well as in developing countries.

In countries with low disease incidence, clinicians may not consider the diagnosis. Prior antibiotic treatment can prevent recovery of the organism. Because the disease is very rare in developed countries, most clinicians will never have seen a case of diphtheria in their lifetime.


The National Notifiable Diseases Surveillance System conducts national surveillance for diphtheria. CDC also identifies cases by requests for diphtheria antitoxin (DAT); since 1997, DAT is available for U.S. healthcare professionals only through CDC.

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Page last reviewed: February 26, 2019