Diphtheria

Diphtheria is an infectious disease caused by strains of the bacterium Corynebacterium diphtheriae which produce a toxin capable of inhibiting cellular functions and in particular those of the cells of the heart, kidney and nervous system.

Transmission routes

The infection can occur following direct contact with a patient or a carrier or, more rarely, by indirect contact through contaminated objects.

Symptoms and complications

The incubation period ranges from 1 to 7 days.

The disease affects almost every mucous membrane and based on its location it can be classified as below:

  • Diphtheria rhinitis: characterised by mucus-purulent nasal leaks that can be stained with blood. A white membrane usually forms on the nasal septum. Evolution is benign because diphtheriatoxin remains localised at the nasal level and does not spread around the body.
  • Diphtheria pharyngitis: this is the most frequent localisation. The first symptoms are malaise, sore throat, loss of appetite, low-grade fever. After 2-3 days, a bluish-white membrane forms, surrounded by an erythematous halo, covering part of the soft palate. The membrane sticks to the tissues and bleeds if removed. If the membrane is large, it can cause respiratory obstruction. Patients with a severe case of the disease may develop a marked swelling under the jaw and in front of the neck giving a "bull neck" appearance.
  • Diphtheria laryngitis: this can manifest due to an extension of a previous form or may affect only the larynx. The symptoms include fever, hoarseness, canine cough. Membrane formation in the larynx can cause airway obstruction.
  • Cutaneous diphtheria: this is very rare and occurs mainly in tropical areas with gangrenous manifestations
  • Other sites affected are the conjunctiva, the vulvo-vaginal area or the external auditory canal.

The disease generally has a benign course and its severity depends on the spread of the toxin. Complications affect the respiratory system (airway obstruction), the heart (myocarditis), the kidneys (renal failure) and the nervous system (peripheral neuropathy). Fatality ranges from 3% to 23% depending on the clinical form and the possibility of treatment.

The treatment consists in the immediate administration of diphtheria antitoxin and antibiotics (erythromycin or penicillin) and the patients must be put in isolation to avoid affecting other people, a danger that disappears after 2 days of treatment.

Impact on the population

The incidence of the disease worldwide has been decreasing since 1980-1981 coinciding with the increase in vaccination coverage. In 2011, a total of 4,880 cases were reported to the WHO compared to 97,164 in 1980 (Figure 1).

Figura 1

Figura 1. Incidence of diphtheria in the world 1980-2011 (bars) and the trend of vaccination coverage
(the blue line indicates official data reported by the countries, the red line the estimates of WHO and UNICEF).

In the United States, there were about 100,000-200,000 cases of diphtheria and 13,000-15,000 deaths a year before the introduction of vaccination. Since the vaccine was introduced in the late 1940s, cases have rapidly decreased. Between 1970-1979 about 196 cases were reported a year. From 1980 to 2004, a total of 57 cases were reported (2-3 cases per year).

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