Two primary transmission modes are Direct and Indirect. Which option correctly lists them?

Two primary transmission modes are Direct and Indirect. Which option correctly lists them?

• A. Direct and Indirect
• B. Airborne and Contact
• C. Vertical and Horizontal
• D. Zoonotic and Vector-borne

Answer: (A)

Direct and indirect are the two broad modes of disease transmission. Direct transmission means the infectious agent moves straight from an infected person or animal to a susceptible one without an intermediate object or organism, such as through close contact or droplets that spread during coughing or sneezing. Indirect transmission involves an intermediary, like a contaminated surface (fomite), food or water, airborne particles, or a vector such as a mosquito. The option that lists direct and indirect together matches these two overarching categories precisely, making it the best choice. The other options describe specific routes or alternative frameworks (for example, airborne and contact are particular routes, vertical and horizontal refer to generation or direction, and zoonotic and vector-borne focus on sources or vectors rather than the fundamental direct/indirect split).

Direct and indirect are the two broad modes of disease transmission. Direct transmission means the infectious agent moves straight from an infected person or animal to a susceptible one without an intermediate object or organism, such as through close contact or droplets that spread during coughing or sneezing. Indirect transmission involves an intermediary, like a contaminated surface (fomite), food or water, airborne particles, or a vector such as a mosquito. The option that lists direct and indirect together matches these two overarching categories precisely, making it the best choice. The other options describe specific routes or alternative frameworks (for example, airborne and contact are particular routes, vertical and horizontal refer to generation or direction, and zoonotic and vector-borne focus on sources or vectors rather than the fundamental direct/indirect split).