MX1 and influenza: The interference with the replication of influenza by co-infection with SARS-CoV-2 can be attributed to the upregulation of MX1 gene expression by SARS-CoV-2 infection, where MX1 inhibited the replication of the influenza A virus while the upregulation of MX1 by influenza infection did not affect the replication of SARS-CoV-2 [21].