Glossary of Medical and Health Terms

Diphtheria

Diphtheria is an upper respiratory tract illness characterized by sore throat, low fever, and an adherent membrane (a pseudomembrane) on the tonsils, pharynx, and/or nasal cavity. A milder form of diphtheria can be restricted to the skin. It is caused by Corynebacterium diphtheriae, a facultatively anaerobic Gram-positive bacterium. Diphtheria is contagious, spread by direct physical contact or breathing in the aerosolized secretions of infected individuals. Once quite common, diphtheria has largely been eradicated in developed nations through widespread vaccination. In the U.S. for instance, there were 52 reported cases of diphtheria between 1980 and 2000; since 2000 there have only been five cases as the DPT (Diphtheria-Pertussis-Tetanus) vaccine is given to all school children.

Boosters of the vaccine are recommended for adults since the benefits of the vaccine decrease with age without constant re-exposure; they are particularly recommended for those travelling to areas where the disease has not been eradicated. In the 1920s there were an estimated 100,000 to 200,000 cases of diphtheria per year in the United States, causing 13,000 to 15,000 deaths. Children represented a large majority of these cases and fatalities. The first successful vaccine for diphtheria was developed in 1923. However, antibiotics against diphtheria were not available until the discovery and development of sulfa drugs following World War II. The Schick test, invented between 1910 and 1911, is a test used to determine whether or not a person is susceptible to diphtheria. It was named after its inventor, Béla Schick (1877-1967.)

The respiratory form has an incubation period of 2-5 days. The onset of disease is usually gradual. Symptoms include fatigue, fever, a mild sore throat and problems swallowing. Children infected have symptoms that include nausea, vomiting, chills, and a high fever, although some do not show symptoms until the infection has progressed further. In 10% of cases, patients experience neck swelling. These cases are associated with a higher risk of death. In addition to symptoms at the site of infection (sore throat), the patient may experience more generalized symptoms, such as listlessness, pallor, and fast heart rate. These symptoms are caused by the toxin released by the bacterium. Low blood pressure may develop in these patients. Longer-term effects of the diphtheria toxin include cardiomyopathy and peripheral neuropathy (sensory type). The cutaneous form of diphtheria is often a secondary infection of a pre-existing skin disease. Signs of cutaneous diphtheria infection develop an average of seven days after the appearance of the primary skin disease. The current definition of diphtheria used by the Centers for Disease Control and Prevention (CDC) is based on both laboratory and clinical criteria.

• Laboratory criteria: isolation of Corynebacterium diphtheriae from a clinical specimen, or histopathologic diagnosis of diphtheria.
• Clinical criteria: upper respiratory tract illness with sore throat, low-grade fever, and an adherent pseudomembrane of the tonsil(s), pharynx, and/or nose.

The disease may remain manageable, but in more severe cases lymph nodes in the neck may swell, and breathing and swallowing will be more difficult. People in this stage should seek immediate medical attention, as obstruction in the throat may require intubation or a tracheotomy. In addition, an increase in heart rate may cause cardiac arrest. Diphtheria can also cause paralysis in the eye, neck, throat, or respiratory muscles. Patients with severe cases will be put in a hospital intensive care unit (ICU) and be given a diphtheria anti-toxin. Since antitoxin does not neutralize toxin that is already bound to tissues, delaying its administration is associated with an increase in mortality risk. Therefore, the decision to administer diphtheria antitoxin is based on clinical diagnosis, and should not await laboratory confirmation. Antibiotics have not been demonstrated to affect healing of local infection in diphtheria patients treated with antitoxin. Antibiotics are used in patients or carriers to eradicate C. diphtheriae and prevent its transmission to others. The CDC recommends either:

• Erythromycin (orally or by injection) for 14 days (40 mg/kg per day with a maximum of 2 g/d), or
• Procaine penicillin G given intramuscularly for 14 days (300,000 U/d for patients weighing <10 kg and 600,000 U/d for those weighing >10 kg).

Patients with allergies to penicillin G or erythromycin can use rifampin or clindamycin.

Diphtheria is a serious disease, with fatality rates between 5% and 10%. In children under 5 years and adults over 40 years, the fatality rate may be as much as 20%. Outbreaks, though very rare, still occur worldwide, even in developed nations. After the breakup of the former Soviet Union in the late 1980s, vaccination rates in its constituent countries fell so low that there was an explosion of diphtheria cases. In 1991 there were 2,000 cases of diphtheria in the USSR. By 1998, according to Red Cross estimates, there were as many as 200,000 cases in the Commonwealth of Independent States, with 5,000 deaths. This was so great an increase that diphtheria was cited in the Guinness Book of World Records as "most resurgent disease".

Associated ICD-10 codes: A30.

Source: http://en.wikipedia.org/wiki/Diptheria

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