In some cases, the messenger RNA (mRNA) levels of known receptors explained viral entry satisfactorily, such as angiotensin converting enzyme (ACE) 2 for SARS-CoV-2, nectin 4 for measles, dipeptidyl peptidase (DPP) 4 for MERS-CoV (Middle East respiratory syndrome coronavirus), and Ephrin (EFN) B2 for Nipah virus pseudotypes (P < 0.001 in all cases; Fig. 5a and Extended Data Fig. 4). Here, ACE is linked to measles.