Genetic drift of MERS-CoV in Saudi Arabia during 2012-2019.

Middle East respiratory syndrome (MERS) is caused by MERS-CoV that infects both human and camel. Camel is supposed to be the natural reservoir for human infection while the sources for most of the primary human infection cases are still not known. We identified two conserved pyrimidine nucleotides that flank UAAU element in MERS-CoV 5'-UTR. These conserved pyrimidine nucleotides distinguish MERS-CoVs into 3 types, that is, UUAAUU, CUAAUU and CUAAUC (referred to as U----U, C----U, and C----C types, respectively). Human MERS-CoV displays a genetic drift from U----U, C----U, to C----C from 2012 to 2019. Camel virus displays a genetic drift from U----U to C----U with a time lag when compared with human virus. The discrepancy in genetic drift seems not to support the notion that camel serves as the only natural reservoir for human infection.