What is the defining characteristic of reservoir hosts in disease ecology?

• A. Transmit infectious agents by aerosol spread of direct contact, but not by indirect contact
• B. Never show clinical signs of infection
• C. Serve as a habitat in which the pathogen can survive
• D. Almost always show clinical signs of infection

Answer: (C)

Reservoir hosts are defined by their role in maintaining and persisting the pathogen in the natural environment. The crucial idea is that the host provides a habitat or ecological niche where the agent can survive over time, allowing continued transmission to other susceptible hosts even when outbreak levels are low. This maintenance often occurs with subclinical or inapparent infections, so the reservoir may not show obvious disease, though it can in some cases. The defining feature is the pathogen’s persistence in nature, not the specific way it is transmitted or the host’s disease status. For example, a species that harbors a pathogen long-term and serves as a continual source for spillover fits as a reservoir, whereas transmission routes (airborne, direct contact, indirect contact) describe how spread occurs but do not define the reservoir role.