Emergence of toxigenic Corynebacterium diphtheriae infections in low-risk patients in Switzerland - report of an outbreak investigation

We report a cluster of toxigenic Corynebacterium diphtheriae infections in Switzerland, affecting patients considered at low risk due to the absence of exposure or travel. Two of the patients were elderly, one of which succumbed to respiratory diphtheria, while the other two recovered from cutaneous diphtheria. Two C. diphtheriae isolates were genetically identical and related to isolates sequenced within the context of an outbreak among refugees mainly from Syria and Afghanistan. Despite extensive investigations, no epidemiological link could be established.