A proliferation of pathogens through the 20th century

A substantial proportion of immunologists, microbiologists and health professionals – and, indeed, many dictionaries – currently regard the term pathogen as a synonym for a pathogenic organism (most often a micro-organism). I will argue that this is a distortion of its original meaning –'a specific causative agent of disease'. An analysis of the historical use of the term pathogen together with a comparison of the meanings of pathogen, pathogenic and pathogenesis suggest that this was an insidious change. It began as a convenient abbreviation, escalated into a misappropriation and is now lodged in bio-medicine's popular lexicon. In science, we should resist the pressures brought about by the mass action of common usage – unless there is a good, logical reason to accept this change. I propose that this common usage results in a distortion and leads to conceptual confusion, particularly when we try to understand the interaction between hosts and invasive organisms. This drift, in which pathogen becomes exclusively a living organism, is corrupting. There is a strong case for correcting and reversing it.