– An acute, highly communicable disease affecting the mucous membranes of the respiratory tract.
Causes and Incidence
Diphtheria is caused by the gram-positive rod Corynebacterium diphtheriae and is spread by direct contact with an infected person, carrier, or contaminated articles or surfaces, particularly in crowded and poorly maintained environments. Effective immunization efforts have made this disease rare in many parts of the world. However, the incidence has been increasing since the early 1970s, especially in the Pacific Northwest, and children under 15 years of age are particularly vulnerable.
The pathogen invades and multiplies in the nasopharynx, producing a toxin that causes necrosis of the epithelial membrane and forming a patchy, grayish green pseudomembrane comprising bacteria, fibrin, leukocytes, and necrotic tissue. The toxin is spread systematically by the bloodstream, and lesions form in distant organs, including the lungs, heart, kidneys, and central nervous system. The individual is communicable from exposure until the bacilli are no longer present (2 to 4 weeks). Cutaneous diphtheria, characterized by skin lesions, is also common.
The incubation period is 1 to 4 days; the first symptoms include a mild sore throat, nasal discharge, dysphagia, low-grade fever, cough, hoarseness, nausea, vomiting, and chills. A grayish green membrane forms on the nasal mucosa, soft palate, nasopharynx, larynx, and tonsils. If a respiratory obstruction develops, dyspnea, stridor, retractions, hypoxia, and cyanosis may be evident.
Severe complications are common without prompt treatment; they include myocarditis, heart failure and sudden death, polyneuritis, encephalitis, renal failure, cerebral infarction, thrombophlebitis, pulmonary emboli, respiratory paralysis, pneumonia, and respiratory failure.
Clinical evaluation and characteristic clinical signs, particularly the membrane, are used for tentative diagnosis. Definitive diagnosis is made by culture of the causative agent.
Tracheostomy for airway obstruction.
Diphtheria-tetanus-pertussis immunization for all children, with periodic diphtheriatetanus toxoid boosters through adulthood for prevention; immunization of close contacts, including health care personnel; diphtheria antitoxin given promptly on clinical diagnosis; antiinfective drugs to kill the causative gram-negative bacteria.
Isolation; bed rest progressing to restricted activity; oxygen; fluid replacement if needed; cultures until three negative results are achieved; cultures of close contacts.