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Diphtheria - Causes, Symptoms and Treatment
Diphtheria is an acute, highly contagious toxin-mediated infection caused by corynebacterium diphtheriae, a grampositive rod that usually infects the respiratory tract, primarily the tonsils, nasopharynx, and larynx, usually producing a membranous pharyngitis. GI and urinary tracts, conjunctivae, and ears are rarely involved.
Thanks to effective immunization, diphtheria is rare in many parts of the world, including the United States. Since 1972, the incidence of cutaneous diphtheria has been increasing, especially in the Pacific Northwest and the Southwest, in areas where crowding and poor hygienic conditions prevail. Most victims are children under age 15; about 10% of patients die. Recent outbreaks have occurred in the newly independent states adjacent to the former Soviet Union.
Causes of Diphtheria
Transmission usually occurs through intimate contact or by airborne respiratory droplets from asymptomatic carriers or convalescing patients; many more people carry this disease than contract active infection. Diphtheria is more prevalent during the colder months because of closer person-to-person contact indoors. But it may be contracted at any time during the year. Humans are the only known reservoir for this bacteria.
Signs and Symptoms of Diphtheria
Most infections go unrecognized, especially in partially immunized individuals. The incubation period for diphtheria is normally 1 week.
Some of the Common Symptoms may be:
- Thick, patchy, grayish-green membrane over the mucous membranes of the pharynx, larynx, tonsils, soft palate, and nose.
- Fever.
- Sore throat.
- A rasping cough.
- Hoarseness.
- Other symptoms may be similar to croup infection.
Attempts to remove the membrane usually cause bleeding, which is highly characteristic of diphtheria. If this membrane causes airway obstruction (especially likely in laryngeal diphtheria), signs include tachypnea, stridor, possibly cyanosis, suprasternal retractions, and suffocation, if untreated. In cutaneous diphtheria, skin lesions resemble impetigo.
Complications include thrombocytopenia, myocarditis, neurologic involvement (primarily affecting motor fibers but possibly also sensory neurons), renal involvement, and pulmonary involvement (bronchopneumonia) due to C. diphtheriae or other superinfecting microbes.
Diagnosis of Diphtheria
Examination showing the characteristic membrane and a throat culture, or culture of other suspect lesions growing C. diphtheriae, confirm this diagnosis.
Treatment for Diphtheria
Treatment must not wait for confirmation by culture. Standard treatment includes diphtheria antitoxin administered I.M. or I.V.; antibiotics, such as penicillin or erythromycin, to eliminate the microbes from the upper respiratory tract and other sites, to terminate the carrier state; measures to prevent complications; and possible tracheotomy if airway obstruction occurs.
Diphtheria infection doesn't confer immunity, therefore diphtheria immunization should be given during convalescence.
Special Considerations and Prevention Tips for Diphtheria
- Serial ECGs should be performed twice weekly for 4 to 6 weeks to watch for myocarditis.
- To prevent spread of this disease, stress the need for strict isolation. Teach proper disposal of nasopharyngeal secretions. Maintain infection precautions until after three consecutive negative cultures at least 24 hours apart, with the first culture being at least 24 hours after the completion of antimicrobial therapy. Treatment of exposed individuals with antitoxin remains controversial. Suggest that family members later receive diphtheria toxoid if they haven't been immunized.
- Give drugs as ordered. Although time consuming and risky, desensitization should be attempted if tests are positive because diphtheria antitoxin is the only specific treatment available. Because mortality increases directly with delay in antitoxin administration, the antitoxin is given before laboratory confirmation of diagnosis if sensitivity tests are negative. Before giving diphtheria antitoxin, which is made from horse serum, obtain eye and skin tests to determine sensitivity. After giving antitoxin or penicillin, be alert for anaphylaxis; keep epinephrine 1: 1,000 and resuscitation equipment handy. In patients who receive erythromycin, watch for thrombophlebitis.
- Monitor respirations carefully, especially in laryngeal diphtheria (usually, such patients are in a high-humidity or croup tent). Watch for signs of airway obstruction, and be ready to give immediate life support, including intubation and tracheotomy.
- Watch for signs of shock, which can develop suddenly.
- Obtain cultures as ordered.
- If neuritis develops, tell the patient it's usually transient. Be aware that peripheral neuritis may not develop until 2 to 3 months after onset of illness.
- Assign a primary nurse to increase the effectiveness of isolation. Give reassurance that isolation is temporary.
- Stress the need for childhood immunizations to all parents. Report all cases of diphtheria to local public health authorities.
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