When infected individuals in an epidemic die (top row), but are regularly replaced with new imports (bottom row), from the pathogen’s perspective this constitutes a steady supply of new susceptible hosts. Epidemiological theory predicts that a situation like this will prolong the duration of an epidemic. An example of this happening in beekeeping is the common habit of replacing dead-outs in an apiary with new nucs or packages from outside sources. One way to ease this problem is to make up dead-outs with splits from the same apiary.
