[gleenn]

I don't think this is nearly as true for virii genomes, but larger species have lots of protetive sections of DNA to protect from mutations. If you lose a non-protein-coding section of DNA to mutation, no harm to the species occurs. In humans, only about 1.5% of our DNA codes for protein that is actually generated. Virii are physically extremely tiny in terms of cell size and must be very efficient in terms of storing the DNA within them so way more actually codes, but no doubt there are similar factors at play.

[flobosg]

Viral genomes are very compressed. In fact, viruses usually have overlapping genes, where one genomic region can codify for more than one product. See the following review for more information: https://www.nature.com/articles/s41576-021-00417-w