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- Acute respiratory tract infection typically causing a membranous pharyngitis by gram-positive facultative anaerobic bacterium Corynebacterium diphtheriae
- Incubation period 2 to 5 days (range 1 to 10 days)
- Infection peaks in fall and winter in temperate regions:
- Seasonal trends are less distinct in the tropics.
- Cutaneous form peaks in August to October in Southern United States.
- Transmission by respiratory spread from infected person or carrier
- Humans are the only reservoir.
- Rarely transmitted directly from skin lesions or contaminated fomites
- Several forms occur:
- Membranous pharyngotonsillar diphtheria
- Nasal diphtheria
- Obstructive laryngotracheitis
- Cutaneous diphtheria
- System(s) affected: cardiovascular, nervous, skin/exocrine, respiratory
- Predominant age: children <15 years and poorly immunized adults
- Predominant sex: male = female
- United States: noncutaneous form, 1.6 in 100 million
- Diphtheria rare in the United States
- Worldwide in 2016: 7,101 cases reported to the World Health Organization (WHO)
- Recent outbreaks have occurred in Brazil, West-Africa, Ukraine, Poland, India, New Zealand, and the tropical Polynesian Islands.
Etiology and Pathophysiology
Toxigenic strains of C. diphtheriae produce an exotoxin that inhibits protein synthesis in all cell types. Toxin causes local damage and necrosis of the pharyngeal membranes, leading to the Greek name “diphtheria,” translated as “leather hide.” Toxin is absorbed and disseminated hematogenously and can lead to myocarditis and neuritis.
- Crowded living conditions
- Inadequate immunization
- Lower socioeconomic status
- Native American ethnicity
- Travelers: Outbreaks have occurred in various countries; see CDC travel Web site.
Immunization: diphtheria toxoid (inactivated toxin)
- Primary series of five immunizations. Children should receive doses at 2, 4, 6, 15 to 18 months and 4 to 6 years of age with 0.5 mL of DTaP vaccine IM. If the pertussis component is contraindicated, then pediatric diphtheria tetanus (DT) should be used. A booster dose of adult Tdap should be given at 11 to 12 years.
- Due to the rise in pertussis, new Advisory Committee on Immunization Practices recommendations include a Tdap dose during each pregnancy (regardless of prior immunizations), ideally given between 27 and 36 weeks’ gestation is now recommended.
- Unimmunized persons ≥7 years should receive 2 doses of adult Td 4 to 8 weeks apart, with a 3rd dose 6 to 12 months later. 0.5 mL of Td should be given. Subsequently, booster doses with Td should be given every 10 years to all individuals without a contraindication. CDC currently recommends that Tdap substitute for one of the recommended decennial Td boosters.
- Immunized individuals may develop a milder course of diphtheria; immunization protects against the toxin, not infection or microbial carriage in the nose, pharynx, or skin.
- Close contacts should be cultured and given antibiotic prophylaxis, regardless of immunization status.
- Contacts should receive a diphtheria toxoid–containing vaccine unless vaccinated within the past 5 years.