I can see that explanation working in a comic book science way, but that is not how it's explained at all. It's basically explained as, heat makes it stronger, so the sun makes it very strong. The virus was able to live longer in Apollo though, but that had more to do with Apollo being resistant to disease than the virus taking on his strength.
To be fair, it's only being called a virus by the characters who don't know everything about it yet and could in fact end up being an entity that's supposed to be kind of like "God" from a previous Authority story, but it hasn't really been explained in detail yet.
Still, the thing does basically act like a virus, so I don't know. Perhaps all silliness will be handwaved away.