In the chain of infection, the mode of transmission describes

• A. The route by which a pathogen enters a new host
• B. The place where pathogens are kept
• C. The method by which a pathogen spreads from reservoir to host
• D. The duration of illness

Answer: (C)

The mode of transmission is the mechanism by which a pathogen moves from its reservoir to a susceptible host. It describes how the infectious agent is spread, not where it enters the body or how long illness lasts. For example, direct contact or droplet spread transfers the pathogen through close physical contact or short-range airborne particles; airborne spread allows tiny particles to remain suspended and travel farther; vehicle transmission involves contaminated objects, food, water, or blood; vector-borne transmission uses another organism, like a mosquito, to carry the pathogen. Understanding this helps explain why certain control measures—hand hygiene to reduce direct contact, masks or ventilation to limit airborne spread, proper food and water safety, sterilization of instruments, and vector control—are effective at interrupting transmission.