Ace the Missouri Basic Skills Test 2026 – Boost Your Brains and Conquer the Challenge!

The chain of infection. This idea connects six parts to explain how disease spreads: the infectious agent is the germ that can cause illness; the reservoir is where that germ lives and multiplies; the portal of exit is how it leaves that place; the mode of transmission is the way it moves to a new person; the portal of entry is how it gets into a new person; and the susceptible host is someone who can be infected because their defenses are lowered or they haven’t been protected by immunity or vaccination. Understanding this chain helps you see where to intervene—stopping transmission with practices like hand hygiene, proper cleaning, and vaccination breaks one or more links, preventing the spread. Other terms like transmission pathway or disease cycle describe parts of the process or use a different focus, but the standard framework that ties all six elements together is the chain of infection.