An infectious disease caused by the bacteria Corynebacterium diphtheriae. Diphtheria is transmitted from person to person, usually via respiratory droplets. The most notable feature of diphtheria infection is the formation of a thick gray substance called a pseudomembrane over the nasal tissues, tonsils, larynx, and/or pharynx.

A vaccine made from sections of a pathogen’s DNA. Once injected, the host creates proteins that stimulate an immune response against the pathogen. Several veterinary DNA vaccines are licensed in the United States.