In zoonotic transmission, which can serve as a reservoir?

• A. An environment or animal population where the pathogen persists
• B. A human host who becomes ill
• C. A vector organism
• D. A vaccine

Answer: (B)

In zoonotic transmission, the reservoir is the environment or animal population where the pathogen can persist over time and serve as the source for infection to others. Humans typically are not reservoirs; we usually act as incidental or dead-end hosts and do not maintain the pathogen in a continuing transmission cycle. A vector is simply a means of transmission, not a place or population that sustains the pathogen, and a vaccine is not involved in maintaining a pathogen in nature. For many zoonoses, the pathogen persists in animal hosts or in the environment, and those reservoirs are what enable spillover to humans.