ACE2 and infection: Co-infection or pre-infection with the H3N2 virus had no effect on the replication of SARS-CoV-2 in Syrian hamsters [21], while pre-infection or co-infection with pandemic H1N1 reduced the replication of SARS-CoV-2 in A549-ACE2 cells [10] in ferrets [22] and in golden Syrian hamsters [23].