Which statement best defines vector-borne transmission?

• A. Transmission via a vector that mechanically or biologically carries the pathogen.
• B. Transmission via contaminated water.
• C. Transmission via direct contact.
• D. Transmission via airborne droplets.

Answer: (A)

Vector-borne transmission happens when a vector carries and transmits a pathogen to a new host, either by the pathogen developing inside the vector or simply being carried on the vector’s body. In biological transmission, the pathogen multiplies or matures within the vector (for example, malaria parasites or dengue virus in mosquitoes) before being passed to a person. In mechanical transmission, the vector doesn’t support the pathogen’s life cycle; instead, the pathogen is carried on the vector’s body or mouthparts and transferred during contact (like a fly picking up bacteria from waste and touching a person or food). This concept is distinct from other routes of spread: contaminated water transmits disease via the environment (waterborne), direct contact involves person-to-person touch or fluids, and airborne droplets spread pathogens through the air from coughing or sneezing. So the defining idea is that the vector is involved in carrying and delivering the pathogen, either biologically or mechanically.