Which term describes the degree of pathogenicity of a microorganism?

The term that describes the degree of pathogenicity of a microorganism is virulence. Virulence specifically refers to the severity or harmfulness of a pathogen and its ability to cause disease. It encompasses various factors that contribute to the microorganism's capacity to cause illness, such as its ability to invade hosts, evade the immune system, and produce toxins.

Infectivity refers to the ability of a pathogen to establish an infection in a host, which does not necessarily correlate to the severity of the disease it may cause. Pathogenicity is a broader term that encompasses the overall ability of an organism to cause disease, but it does not specifically indicate the level of harm that can result. Toxicity refers to the ability of a substance to cause damage to biological systems, which may involve the production of toxins by microorganisms but does not fully encompass the concept of pathogenicity. Thus, virulence is the most accurate term for describing how pathogenic a microorganism can be.