| Noun | 1. | infective agent - an agent capable of producing infection virus - (virology) ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein pathogen - any disease-producing agent (especially a virus or bacterium or other microorganism) agent - an active and efficient cause; capable of producing a certain effect; "their research uncovered new disease agents" |