Which term describes an organism that can carry pathogens and transmit them to others?

• A. Host
• B. Carrier
• C. Reservoir
• D. Vector

Answer: (D)

A vector is an organism that transmits pathogens from one host to another. Vectors are often biting insects like mosquitoes, ticks, or fleas. The pathogen may multiply inside the vector (biological transmission) or be carried on its body (mechanical transmission) and then passed to a new host during feeding or contact. This role of moving the pathogen between hosts is what makes the term vector the best fit. A host is the organism that becomes infected, a reservoir is a source where the pathogen persists, and a carrier is someone who harbors and can spread the pathogen, but these terms don’t specifically describe the transmission between hosts the way vector does.