Which term refers to the spread of a disease-causing agent from one host to another?

• A. Infection
• B. Contagion
• C. Transmission
• D. Spread

Answer: (C)

Transmission is the process by which a disease-causing agent is passed from one host to another. It specifically describes how the pathogen moves between individuals, via direct contact, droplets or aerosols, vectors, or contaminated surfaces.

Infection refers to what happens after the pathogen has entered a host and begins to multiply, not the transfer between hosts. Contagion is often used to describe how easily a disease can spread, or the disease itself in common language, but it’s less precise about the mechanism of transfer. Spread is a broad term that doesn’t specify the biological process involved.

So, the best term for the act of moving the pathogen from one person to another is transmission.