Prognosis

Mechanical respiratory obstruction and myocarditis account for most diphtheria-related deaths.[27] The overall case fatality rate for diphtheria was 2.4% in the 1940s and remained at 2% to 3% in the Russian outbreak of the 1990s. If diphtheric polyneuropathy develops, mortality of 16% has been reported.[61]

Before the era of effective treatment, the case-fatality rate was approximately 50%; with treatment and vaccination more widely available, the case-fatality rate has remained at approximately 10%.[1]​ In 2017-2019, the largest diphtheria outbreak of the current century, among Rohingya refugees in Bangladesh, was associated with a much lower mortality rate of 0.5%.[22][23]

Recovery of cardiac function is usually complete following myocarditis. However, patients who experience severe arrhythmias may sustain permanent damage to the cardiac conduction system.[4]​

Usually there is complete resolution of neurologic deficits. Rarely, dysfunction of the vasomotor centers can lead to hypotension and heart failure.[4]​

Patient age and immunization status are important prognostic factors: very old and very young people generally have a poorer prognosis, while previous immunization is associated with a better prognosis.

The timing of diphtheria antitoxin therapy is crucial to outcome; early administration can prevent many of the toxic sequelae of the disease.[4]​ Skin infections rarely cause systemic symptoms.​[2]​[3]​​

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