Diphtheria is an acute bacterial infection caused by a Corynebacterium of the diphtheria complex (Corynebacterium diphtheriae, Corynebacterium ulcerans, Corynebacterium pseudotuberculosis). These three species of bacteria are capable of producing diphtheria toxin, the one responsible for clinical manifestations.
Highly contagious, the transmission of Corynebacterium diphtheriae is man-to-man via saliva droplets during direct contact between patients and healthy carriers. The causes of indirect transmission are rarer, but exist: for example, by contact with objects soiled by the sputum of an infected person. The incubation period is of the order of two to five days.
In France (excluding Mayotte), only 8 cases of Corynebacterium diphtheriae infection have been recorded since 2004. All were imported cases, contaminated during stays outside France, particularly in the countries concerned endemic or outbreaks . Among them: the former USSR, Algeria, Ecuador, Thailand, Afghanistan, Djibouti, etc.
As for the Corynebacterium ulcerans infection, it is transmitted by ingestion of raw milk or by contact with pets, themselves often asymptomatic. In the case of C. ulcerans infections, there has never been any transmission from man to man has ever been observed.