What is diphtheria?

Causes and Symptoms

The etiological agent of diphtheria, Corynebacterium diphtheriae, is found in some individuals as an inhabitant of the nasopharynx (nose and throat). Its symptoms are associated with the production of a toxin. Only those strains of the organism carrying a bacteriophage in a lysogenic state produce the toxin. Spread of diphtheria is generally person to person through respiratory secretions or through contaminated environmental surfaces.

Following an incubation period of several days to a week, symptoms often have a sudden onset and typically include a sore throat, malaise, and a mild fever. The disease is further characterized by an exudative, pseudomembrane formation on the mucous surface of the throat, which results from replication of the organism in the pharynx or surrounding areas. The pseudomembrane can become quite thick and may cause respiratory stress through obstruction of the breathing passages. Toxin is secreted into the bloodstream, where its presence can result in damage to the heart, nervous system, or other organs. Diagnosis is based upon a combination of symptoms, as well as isolation of the organism in a throat culture.

A less common form of diphtheria may be observed on skin surfaces. It contains bacteria that can be spread through contaminated environmental surfaces. Infection generally occurs through small cuts in the skin. Cutaneous diphtheria is characterized by an ulcer that heals slowly. If the organism is a strain that produces toxin, then systemic damage may result.

Treatment and Therapy

Most diphtheria infections respond to antibiotics, either a single dose of penicillin or a seven-day or ten-day course of erythromycin. Since symptoms are associated with toxin production, the administration of antitoxin is critical to early treatment. Once toxin has been incorporated into the target, cell death is irreversible. Antibiotic treatment, however, does result in the elimination of the organism and the termination of further toxin production.

Vaccination with diphtheria toxoid, an inactivated form of the toxin, has proven effective in immunization against the disease. Prophylaxis is generally started early in childhood as part of the trivalent DPT (diphtheria, pertussis, tetanus) series. Boosters are recommended at ten-year intervals.

Perspective and Prospects

Introduction of the diphtheria vaccine in the first decades of the twentieth century served to reduce significantly the incidence of the disease in the West. The use of antibiotic therapy further reduced the fatality rate associated with this disease, which ranged from 30 to 50 percent at its peak. Diphtheria is almost unknown in the United States in the twenty-first century, with only five reported cases in the first decade, according to the Centers for Disease Control. The disease still exists as a childhood scourge in the developing world, although fewer than 5,000 cases were reported worldwide in 2011, according to the World Health Organization.

Bibliography

Atkinson, William, Charles Wolfe, and Jennifer Hamborsky, eds. "Diphtheria." In Epidemiology and Prevention of Vaccine-Preventable Diseases. 12th ed. Washington, D.C.: Centers for Disease Control and Prevention, 2011.

Grob, Gerald N. The Deadly Truth: A History of Disease in America. Cambridge, Mass.: Harvard University Press, 2002.

Martin, Julie J. "Diphtheria." Health Library, January 7, 2013.

Parker, James N., and Philip M. Parker, eds. The Official Patient’s Sourcebook on Diphtheria. San Diego, Calif.: Icon Health, 2002.

World Health Organization. "Diphtheria." World Health Organization, September 27, 2012.