Contagium

Contagium is a Latin noun meaning “a thing that is contagious” and is used in historical medical literature to denote the contagious agent or the property of contagion itself. In English-language texts, the term is now largely obsolete, with modern terminology preferring contagion, contagiousness, or pathogen to describe the infectious agent or the process of transmission.

Historical usage centers on debates about the nature of contagious disease in the 18th and 19th centuries. A notable variant was the concept of contagium vivum fluidum (living contagious fluid), associated with Antoine Bechamp, who argued that contagion spread through a living fluid containing microscopic particles called microzymes, capable of giving rise to microbes under certain conditions. This view stood in tension with the germ theory of disease, which attributed contagion to discrete microorganisms.

In contemporary science, contagium survives mainly in historical or philosophical discussions of disease theory. The current vocabulary emphasizes pathogens and infectious agents, routes of transmission, and mechanisms of infection, rather than the older notion of a universal “contagium.” The term highlights how scientific concepts of contagion have evolved from fluidic or intrinsic substances to a framework based on identifiable microorganisms and their interactions with hosts.

See also:

- Contagion

- Germ theory

- Pathogen

- Infectious agent