Diphtheria

Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks, the mortality rate approaches 10%. Signs and symptoms may vary from mild to severe, and usually start two to five days after exposure. Symptoms often develop gradually, beginning with a sore throat and fever. In severe cases, a grey or white patch develops in the throat called a pseudomembrane. This tough, leathery membrane slowly blocks the airway. Starting with a barking cough, similar to that observed in croup, the neck may also swell, in part due to the enlargement of the facial lymph nodes. The pseudomembrane can grow to cover a wide area of the throat, leading to strangulation and death. Diphtheria can also involve the skin, eyes, or genitals, and can cause complications, including myocarditis (which in itself can result in an abnormal heart rate), inflammation of nerves (which can result in paralysis), kidney problems, and bleeding problems due to low levels of platelets. Diphtheria is usually spread between people by direct contact, through the air, or through contact with contaminated objects. Asymptomatic transmission and chronic infection are also possible. Different strains of C. diphtheriae are the main cause in the variability of lethality. The lethality and symptoms themselves are caused by the exotoxin produced by the bacteria. Diagnosis can often be made based on the appearance of the throat, with confirmation by microbiological culture. Previous infection may not protect against reinfection. A diphtheria vaccine is effective for prevention and is available in several formulations. Three or four doses, given along with tetanus vaccine and pertussis vaccine, are recommended during childhood. Further doses of the diphtheria–tetanus vaccine are recommended every ten years. Protection can be verified by measuring the antitoxin level in the blood. Diphtheria...