Diphtheria is a communicable disease caused by infection with Corynebacterium diphtheriae, typically presenting as respiratory tract infection in temperate climates and as cutaneous infection in the tropics. Clinical manifestations include pseudomembrane formation in the respiratory tract and soft tissue swelling of the neck ("bull neck"). Serious complications, primarily damage to the heart muscle and certain nerves that activate muscles, are due to diphtheria toxin, a potent toxin. Nontoxigenic strains can produce respiratory tract illness with pseudomembrane. Clusters of cases of invasive disease due to nontoxigenic strains, predominantly among persons with antecedent injection use, have been reported recently from several countries.
Vaccines composed of inactivated diphtheria toxin—diphtheria toxic—were developed in the early twentieth century and have been widely used in most developed countries since the middle of the twentieth century. Prior to introduction of vaccination, diphtheria was a major cause of childhood mortality in the United States, but by the 1990s respiratory diphtheria has been virtually eliminated in the United States and in other countries with high levels of childhood vaccination for diphtheria. Nonetheless, the infection remains endemic in much of the developing world. In the 1990s, a massive resurgence of diphtheria occurred in the countries of the former Soviet Union. Factors contributing to the epidemic included low vaccination coverage among children, lack of routine adult booster vaccination, population movements, and multiple introductions from areas where diphtheria remained endemic.
In the World Health Organization's Expanded Programme on Immunization, diphtheria toxic is administered with tetanus toxic and pertussis vaccine (DTP) at 6, 10, and 14 weeks of age. Recommendations for subsequent doses vary among countries. In the United States, diphtheria toxic is routinely administered with tetanus toxic and acellular pertussis vaccine at 2, 4, and 6 months of age, with booster doses at 15 to 18 months and 4 to 6 years of age.
Diptheria antitoxin is the mainstay of treatment of diphtheria. Outcome improves with early diagnosis and treatment. Antimicrobial therapy with penicillin or erythromycin hastens elimination of the organism. Antimicrobial prophylaxis is recommended for those in close contact with diphtheria cases.