Acute infectious disease caused by Corynebacterium diphtheriae; affects primarily the membranes of the upper respiratory tract with the formation of a gray-white pseudomembrane


  • The only known reservoir for C. diphtheriae is humans; disease is acquired by contact with either a carrier or a diseased person.
  • Most cases occur during the cooler autumn and winter months in individuals <15 years of age who are unimmunized.
  • Recent outbreaks have occurred, most notably in the countries of the former Soviet Union, and supply additional evidence that disease occurs among the socioeconomically disadvantaged living in crowded conditions.


  • Although the disease is distributed throughout the world, it is endemic primarily in developing regions of Africa, Asia, and South America.
  • In the Western world, the incidence of diphtheria has changed dramatically in the past 50 to 75 years as a result of the widespread use of diphtheria toxoid after World War II.
  • The incidence has declined steadily and is now a rare occurrence.

General Prevention

Active immunization with diphtheria toxoid is the cornerstone of population-based diphtheria prevention. Current recommendations from the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) are as follows:

  • Ages 2 months to 7 years: 5 doses of diphtheria vaccine (with tetanus toxoid and acellular pertussis)
    • First three given as DTaP vaccine 0.5 mL IM at 2-month intervals beginning at 2 months of age
    • Fourth dose of DTaP should be given at 15 to 18 months of age.
    • Fifth dose of DTaP at 4 to 6 years of age
  • In 2005, 2 tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccines were licensed for use in adolescents 11 to 18 years of age.
  • 1 booster dose of Tdap should be given to all adolescents at the 11- to 12-year-old visit, provided they have completed the childhood series. Subsequent tetanus and diphtheria (Td) boosters should be administered every 10 years.
  • Tdap should replace the first dose of Td in children 7 to 10 years of age who are undergoing primary immunization.
  • Isolation of patients with diphtheria is required until culture from the site of infection is negative on two consecutive specimens.


  • The initial entry site for C. diphtheriae is via airborne respiratory droplets, typically the nose or mouth but occasionally the ocular surface, genital mucous membranes, or preexisting skin lesions.
  • Following 2 to 4 days of incubation at one of these sites, the bacterium elaborates toxin.
  • Locally, the toxin induces formation of a necrotic coagulation of the mucous membranes (pseudomembrane) with underlying tissue edema; respiratory compromise may ensue.
  • Elaborated exotoxin may also have profound effects on the heart, nerves, and kidneys in the form of myocarditis, demyelination, and tubular necrosis, respectively.


C. diphtheriae, a gram-positive pleomorphic bacillus

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