As for EV-D68 which did not replicate in the human small intestinal organoids, the mRNA transcript expression level of the receptor intercellular adhesion molecule 5 (ICAM-5) in the organoids was very low (0.49 copies per 104 GAPDH copies) and significantly lower than that in RD cells which are permissive to EV-D68 infection (Figure 3G). Here, GAPDH is linked to infection.