> But why is it less transmissible? One obvious explanation is because we've lived with it all our lives Haven't we lived with different types of coronaviruses

> But why is it less transmissible? One obvious explanation is because we've lived with it all our lives Haven't we lived with different types of coronaviruses all of our lives as well, though? It seems at least equally as plausible that COVID is more transmissible due to actual physical qualities of the virus with respect to replication rate, particle size, and other factors that cause more virus to be expelled from the body in different ways. It could be that the flu is more transmissible by fomites than through aerosols, or that less flu virus tends to be expelled by the body, or that the flu virus has a more difficult time in infecting our cells compared to SARS-CoV2. Of course, this is pure speculation on my part, but from what I can tell we lack data for anyone to be drawing any firm conclusions on this point.