ACVPM Epidemiology and Biostatistics Practice Exam

A carrier is someone who harbors the pathogen, but a reservoir is a source that maintains the pathogen in nature and can continually transmit it to others. An animal can carry a pathogen yet not shed enough of it—or shed only intermittently—to sustain transmission. In other words, carrying the agent does not guarantee the level of pathogen load, the duration of shedding, or the ecological persistence needed for the pathogen to be maintained and repeatedly passed on. Those factors determine whether a host or environment truly acts as a reservoir. Virulence or whether the host shows symptoms are not the defining criteria; asymptomatic carriers can still be reservoirs if they maintain transmission over time.