PERFECT EVOLUTIONARY SUBSTRATE. “Viruses possess all the advantages of evolution relative to host: extreme genetic adaptability, extreme diversity, extreme numbers, extreme rates of genetic exchange, tolerance for ‘unfit’ variation, and the ability to reassemble from cryptic or ‘dead’ parts. They can transition between the chemical and living world.”
http://onlinelibrary.wiley.com/doi/10.1111/apm.12485/full