Diphtheria

Diphtheria is an infectious disease caused by a bacterium which is spread from person to person through coughing and sneezing. This bacterium produces a toxin that can harm or destroy human body tissues and organs. One type of diphtheria affects the throat and sometimes the tonsils. The infection can also affect the skin and, more rarely, mucous membranes at other sites such as the (ear, genitalia and conjunctiva). Diphtheria affects people of all ages, but most often it strikes unimmunized children. In temperate climates, diphtheria tends to occur during the colder months. The disease can be fatal. Between 5% and 10% of diphtheria patients die, even if properly treated. Untreated, the disease claims even more lives. 

The bacteria most commonly infect the respiratory system. Respiratory diphtheria usually occurs after an incubation period of 2–5 days (range 1–10 days). Depending on the anatomical location, respiratory disease may be nasal, pharyngeal, or laryngeal, or any combination of these. Pharyngeal diphtheria is the most common form. The onset is usually relatively slow and characterized by mild fever and exudative pharyngitis initially with progression of symptoms over 2 to 3 days.

In classic cases, the exudate organizes into a pseudo-membrane that gradually forms in the nose, pharynx, tonsils, or larynx. The pseudo-membrane is typically asymmetrical, greyish white in appearance and is firmly attached to the underlying tissue. Attempts to remove the pseudo-membrane result in bleeding at the site. The pseudo-membrane may extend into the nasal cavity and the larynx causing obstruction of the airways, which is a medical emergency that often requires tracheotomy.

Anterior cervical lymph nodes become markedly enlarged and, in some patients, there is considerable inflammation and edema of surrounding tissues (“bull-neck” appearance) with greater morbidity and mortality. Absorption of diphtheria toxin into the bloodstream results in toxic damage to organs such as the heart, kidneys and peripheral nerves. The bacteria can also infect the skin, causing open sores or ulcers. 

The best protection against diphtheria infection is vaccination. WHO recommends a three-dose primary series and three booster doses of diphtheria toxoid-containing vaccine. The recommended schedule of the three-dose primary series is with the first dose administered as early as 6 weeks of age; subsequent doses should be given with an interval of at least four weeks between doses, and the third dose of the primary series should be completed by 6 months of age, if possible. The three boosters should be given in combination with tetanus toxoid at 12–23 months of age, 4–7 years of age and 9–15 years of age, using age-appropriate vaccine formulations. For susceptible exposed individuals, vaccination with diphtheria toxoid-containing vaccine is strongly recommended.