The changing epidemiology of diphtheria in the United Kingdom, 2009 to 2017

Abstract

BackgroundDiphtheria is a potentially fatal disease caused by toxigenic strains of <i>Corynebacterium diphtheriae, C. ulcerans</i> or <i>C. pseudotuberculosis.</i>AimOur objective was to review the epidemiology of diphtheria in the United Kingdom (UK) and the impact of recent changes in public health management and surveillance.MethodsPutative human toxigenic diphtheria isolates in the UK are sent for species confirmation and toxigenicity testing to the National Reference Laboratory. Clinical, epidemiological and microbiological information for toxigenic cases between 2009 and 2017 are described in this population-based prospective surveillance study.ResultsThere were 33 toxigenic cases of diphtheria aged 4 to 82 years. Causative species were <i>C. diphtheriae</i> (n = 18) and <i>C. ulcerans</i> (n = 15). Most <i>C. diphtheriae</i> cases were cutaneous (14/18) while more than half of <i>C. ulcerans</i> cases had respiratory presentations (8/15). Two thirds (23/33) of cases were inadequately immunised. Two cases with <i>C. ulcerans</i> infections died, both inadequately immunised. The major risk factor for <i>C. diphtheriae</i> aquisition was travel to an endemic area and for <i>C. ulcerans,</i> contact with a companion animal. Most confirmed <i>C. diphtheriae</i> or <i>C. ulcerans</i> isolates (441/507; 87%) submitted for toxigenicity testing were non-toxigenic<i>,</i> however, toxin positivity rates were higher (15/23) for <i>C. ulcerans</i> than <i>C. diphtheriae</i> (18/469). Ten non-toxigenic toxin gene-bearing (NTTB) <i>C. diphtheriae</i> were also detected.ConclusionDiphtheria is a rare disease in the UK. In the last decade, milder cutaneous <i>C. diphtheriae</i> cases have become more frequent. Incomplete vaccination status was strongly associated with the risk of hospitalisation and death.