Notes from the Field: Increase in Nontoxigenic Corynebacterium diphtheriae - Washington, 2018-2023

What is already known about this topic? Corynebacterium diphtheriae infections can be caused by toxigenic and nontoxigenic strains. Diphtheria toxoid–containing vaccines (DTaP, Tdap, Td) only protect against toxigenic strains. Nontoxigenic C. diphtheriae infections are most frequently associated with cutaneous disease and are not vaccine preventable. What is added by this report? Review of all Washington nontoxigenic C. diphtheriae cases during a 5-year period revealed that infection prevalence is increasing. Unstable housing and recent illicit substance use were prevalent among patients. Severe disease can manifest as endocarditis and bacteremia. What are the implications for public health practice? Future nontoxigenic C. diphtheriae studies focusing on understanding treatment indications and effectiveness and characterizing modifiable risk factors and barriers to quality wound care might identify opportunities to implement strategies for reducing community spread of C. diphtheriae.