Look up propagule in Wiktionary, the free dictionary.
In biology, a propagule is any material that is used for the purpose of propagating an organism to the next stage in their life cycle via dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by plants (in the form of seeds or spores), fungi (in the form of spores), and bacteria.
In disease biology, pathogens are said to generate infectious propagules, the units that transmit a disease. These can refer to bacteria, viruses, fungi, or protists, and can be contained within host material. For instance, for influenza, the infectious propagules are carried in droplets of host saliva or mucus that are expelled during coughing or sneezing.