Anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies WordNet 3.0 & Open English WordNet

In infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally lives and reproduces, or upon which the pathogen primarily depends for its survival. Wikipedia

The long-term host of the pathogen of an infectious disease Wikipedia Disambiguation

An alternative or passive host for a disease Wikipedia Disambiguation

A living host, such as an animal or a plant, inside of which an infectious pathogen naturally lives and reproduces Wikidata