Detecting diphtheria is not enough: the missing toxigenicity link in outbreak surveillance

Abstract

Diphtheria surveillance in resource-limited settings may stop at clinical diagnosis, organism identification, or molecular detection of the diphtheria toxin gene, although these findings do not provide the same information. Identification of Corynebacterium diphtheriae establishes the organism, tox-gene detection indicates genetic potential for toxin production, and phenotypic testing demonstrates toxin expression. We propose that existing WHO case classifications be retained, while laboratory reports record the level of diagnostic resolution achieved. A tiered system linking peripheral specimen collection, regional culture and molecular testing, and reference-level phenotypic confirmation of selected isolates could strengthen outbreak characterization in Somalia without delaying treatment based on clinical suspicion.