Toxigenic Corynebacterium diphtheriae Infections in Low-Risk Patients, Switzerland, 2023

Abstract

We report a cluster of infections with genetically related toxigenic Corynebacterium diphtheriae linked to an outbreak among asylum seekers in Switzerland that subsequently affected patients without known exposure. This discovery highlights the importance of rapid, interdisciplinary outbreak investigations and regular vaccination status assessment, especially in elderly populations with waning immunity.

Keywords: Corynebacterium diphtheriae; Switzerland; bacteria; diphtheria; outbreak investigation; public health.

Figure

Sequencing data from study of toxigenic Corynebacterium diphtheriae infections in low-risk patients, Switzerland, 2023. Maximum-likelihood single-nucleotide polymorphism (SNP) phylogeny (A) and SNP matrix (B) of C. diphtheriae isolates derived from patient B, patient C, and 5 asylum seekers (AS). Numbers at the tree nodes in panel A denote bootstrap values as percentages from 1,000 replicates; scale bar indicates substitutions per site. Matrix in panel B contains the pairwise number of SNP differences used to generate the tree. We used a 3-color scale, where blue represents lowest values, red highest values, and white intermediate values.