A primary host that harbors the pathogen but shows no ill effects and serves as a source of infection.
Reservoir hosts do not get the disease carried by the pathogen or it is asymptomatic and non-lethal. Once discovered, natural reservoirs elucidate the complete life cycle of infectious diseases, providing effective prevention and control.
Examples are marmots, black rats, prairie dogs, chipmunks and squirrels for bubonic plague.
Compare: paratenic host