a. Biological factors: microorganisms, including genetically modified organisms, cell cultures, human endoparasites and prions that can induce infections, allergy or toxic effects in humans. Microorganisms means: a microbiological unit, cellular or non-cellular, able to replicate or transfer genetic material. Cell culture means: the result of in vitro cultivation of cells from multicellular organisms. b. micro-organism: any cellular or non-cellular microbiological entity capable of replication or of transferring genetic material.