Diphtheria

Definition:

An acute infectious disease caused by the toxin-producing bacteria Corynebacterium diphtheria; it affects the respiratory tract (primarily the larynx, tonsils, and throat) and often the heart, kidneys and nervous system .

Causes, incidence, and risk factors:

Diphtheria is found only in humans and is transmitted by respiratory droplets from infected persons or asymptomatic carriers. The incubation period is 1 to 4 days.

The bacteria primarily infect the nose and throat although they may initially infect the skin producing skin lesions. C. diphtheriae produces a toxin which causes tissue damage (necrosis) in the immediate area of the infection, usually the nose and throat. It can spread via the bloodstream to other organs where it can cause significant damage. Although the toxin can damage any tissue, that of the heart, kidneys and nervous system are most frequently and most severely affected.

The localized infection in the throat and tonsillar area produces a characteristic membrane which is gray to black in color, tough, and fibrous. This membrane can cause airway obstruction.

The disease may be mild and go unrecognized, or it may become progressive. If toxin enters the bloodstream the patient may develop inflammation of the heart muscle (myocarditis) which is the most commonly seen and most worrisome complication. Toxic effects on the nervous system may cause temporary paralysis.

The disease is now rare in many parts of the world because of widespread immunization. Risk factors are crowding, poor hygiene, and lack of immunization. Only 5 cases of diphtheria were reported in the U.S. in 1991. In 1993 and 1994 the separated states of the former USSR experienced a diphtheria epidemic with over 50,000 reported cases. The epidemic was related to a drop in routine childhood immunizations (DPT) to less than 60% compliance.