Final answer:
The correct term for when an infectious agent becomes systemic by spreading throughout the body is 'A. Disseminated infection.' This means the infection affects multiple organs and tissues beyond the initial site of infection.
Step-by-step explanation:
The term that describes the extent of host involvement when an infectious agent breaks loose from a local infection and is carried to other tissues, making the infection systemic, is A. Disseminated infection. When pathogens spread throughout the body often via the bloodstream, they can cause widespread systemic effects. A disseminated infection can also be referred to as a systemic infection because it impacts multiple organs and tissues beyond the initial site of infection.
In penetrating the circulatory system, bacteria or other microbes cause a condition where they may spread rapidly, leading to severe systemic infections. As the microorganisms are transported via the blood vessels, they may reach various parts of the host's body.