Diphtheria is an infectious disease, potentially fatal. It caused by toxigenic bacteria of the Corynebacterium genus, mostly Corynebacterium diphtheriae and rarely other closely related species, namely Corynebacterium ulcerans and Corynebacterium pseudotuberculosis. Diphtheria is re-emerging in areas where population immunity through vaccination has not been maintained. Therefore, both clinicians and laboratory personnel should always maintain a high index of suspicion in patients presenting with signs and symptoms of respiratory or cutaneous diphtheria, particularly after being in countries endemic for the disease. The rarity of cases, as well as the expense and complexity associated with laboratory diagnosis, mean that many countries ceased to screen throat specimens, and therefore, expertise and recognition of the organism have declined. Public health management cannot be effective without the appropriate microbiological diagnosis of the disease.

Over the decades and since the last edition of the manual, many developments in the field of diphtheria happened. The current version revised case definitions and surveillance strategies and includes extensive laboratory diagnostics, molecular technologies, and serology sections. Additionally, the repertoire of infections was extended to all the potentially toxigenic corynebacteria. This laboratory manual will assist the laboratory worker in the correct procedures to diagnose diphtheria cases and guide the clinician in treatment options. The manual is aimed for global use and will hopefully fulfil the needs of all laboratories, including those with minimal resources.