A disease vector is defined as which of the following?

A disease vector is defined as which of the following?

• A. A living organism that transmits disease
• B. A disease-causing microbe
• C. An environmental reservoir
• D. Any agent that acts as a carrier or transporter

Answer: (D)

The main idea is how transmission occurs. A disease vector is defined by its function: it carries and delivers the pathogen to a susceptible host, enabling infection. The statement that this is any agent that acts as a carrier or transporter best captures that role—the essential job of a vector is to move the pathogen from one place (or host) to another. This emphasis on the transfer mechanism explains why it fits as the correct concept: the vector is the vehicle that enables spread of the disease agent to new hosts. Think of it in practice: classic living vectors like mosquitoes or ticks deliver pathogens to people or animals, but the defining point is the transmission action itself—the pathogen is carried and transferred to a new host. The other ideas describe the pathogen itself, or where the pathogen can persist, rather than the means by which it is moved to a new host.

The main idea is how transmission occurs. A disease vector is defined by its function: it carries and delivers the pathogen to a susceptible host, enabling infection. The statement that this is any agent that acts as a carrier or transporter best captures that role—the essential job of a vector is to move the pathogen from one place (or host) to another. This emphasis on the transfer mechanism explains why it fits as the correct concept: the vector is the vehicle that enables spread of the disease agent to new hosts.

Think of it in practice: classic living vectors like mosquitoes or ticks deliver pathogens to people or animals, but the defining point is the transmission action itself—the pathogen is carried and transferred to a new host. The other ideas describe the pathogen itself, or where the pathogen can persist, rather than the means by which it is moved to a new host.