RPS18 and viral infectious disease: The number of reference genes was five in Apis mellifera under different viral infections (IAPV infection: ache2, rps18, β-actin, tbp, and tif; CSBV treatment: rpl14, tif, rpsa, ubc, and ache2; and dsRNA treatment: Rpl14, tif, rps18, ubc, and α-tubulin) [54].