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Diphtheria is an acute infectious disease caused by the bacterium Corynebacteria diphtheriae affecting the upper respiratory tract and occasionally the skin. It is characterised by an inflammatory exudate, which forms a greyish membrane in the respiratory tract. Virulent strains of C. diphtheriae produce a toxin, which can damage heart and nervous tissues. Spread is by droplet infections and through contact with articles soiled by infected persons. An effective vaccine against the disease was introduced in 1940.

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