The human genome is full of viral DNA, but very little of it contributes to our over all physiology and structure. Viruses are mostly an impediment, not a benefit. The ways in which we have adapted to fight viruses and virions are what have made us strong, but the viral particles are mostly nuisances. It's unlikely that panspermia came from a virus. I think smart aliens genetically engineering us makes more sense than that. We have not been able to find the common link between us and our nearest evolutionary relative, yet we have found previous homo species going back millions of years. The first homo sapiens appeared in the Rift Valley 150,000 years ago, give or take. In an evolutionary blink of an eye, we became the most advanced species on the planet. Yet we can't find the missing link between us and the other homo species. That has always struck me as odd.
But then... why would aliens genetically engineer us? To be their slaves? Well, why? Anyone capable of traveling from one star system to another is incredibly advanced. Why would they need us at all? Unless Earth is just one big experiment. I dunno... the intelligent design theory also has holes in it.
Given how humanity keeps making the same ridiculous mistakes over and over, leading to one civilization collapse after another, I am more inclined to believe we are somehow naturally evolved and still imperfectly figuring things out.