In epidemiology, which model describes infection transmission as a set of interconnected processes?

• A. Chain of infection
• B. Epidemiologic triangle
• C. Wheel
• D. Web of infection

Answer: (A)

Infection transmission is best understood as linked steps, which the chain of infection models. It breaks transmission into six components: infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host. Each link has to exist for transmission to occur, so interrupting any one link stops spread. That’s why interventions are framed as breaking the chain: cleaning and disinfection remove the agent from environments, hand hygiene or proper PPE disrupt the mode of transmission, vaccination lowers the number of susceptible hosts, and isolation or barriers prevent exit or entry.

Other models describe disease dynamics in different ways. The epidemiologic triangle focuses on how agent, host, and environment interact to influence risk rather than detailing a stepwise transmission sequence. Wheel or web diagrams exist as alternative visualizations, but they don’t convey the explicit, interdependent chain of steps as directly as the chain of infection.