What term describes the ability of an infectious agent to cause disease?

The term that describes the ability of an infectious agent to cause disease is pathogenicity. Pathogenicity refers to the inherent capability of a microorganism to cause damage to the host and is often assessed by the severity and type of disease it can induce. This concept encompasses various factors, including how the pathogen interacts with the host's immune system and its ability to evade immune responses.

While terms like infectivity, virulence, and transmissibility are related concepts in infectious diseases, they each refer to different aspects. Infectivity refers to the capacity of an agent to enter, survive, and multiply in the host, highlighting how easily an infection can establish itself. Virulence, on the other hand, is a measure of the severity of disease caused by an infectious agent, often influenced by factors such as toxin production and the pathogen's ability to cause damage. Transmissibility is about how easily a disease spreads from one individual to another, emphasizing the mode of transmission rather than the disease-causing capability itself.

Therefore, the correct choice of pathogenicity specifically captures the ability of an infectious agent to cause disease, making it a fundamental concept in understanding infectious diseases.