Thanks for highlighting the co-evolution aspect. I find it more likely that for viruses with a pre-symptomatic phase is the selective pressure caused by the vir

Thanks for highlighting the co-evolution aspect. I find it more likely that for viruses with a pre-symptomatic phase is the selective pressure caused by the virus on the host that ends up resulting in lower severity long term. By simply removing genes from the genepool that were particularly prone to complications. With a pre-symptomatic phase the selective pressure on the virus is towards more infectivity and longer pre-symptomatic phase. Not necessarily towards milder outcomes.