By the Light of the Moon

So, I had an idea. Lycacanthropes are altered by the light of the moon, right? But why not the sun? The moon's light is just a reflection of it.
So I got to thinking. Lycanthropes transmit their affliction through bites and cuts, so let's just assume it's viral or bacterial. Now, certain lifeforms are very dependent on sunlight, or light in general. White light can be divided into the visible spectrum of colors via a prism. So, perhaps the moon's not a ball of relatively inert rock, but actually has a surface covered with crystal formations and the like. When sunlight hits these crystals, they act as a prism, and the newly divided light is reflected back to the Earth's surface where it hits the skin of an individual carrying the virus/bacteria/whatever, agitating it and causing the carrier to transform somehow, perhaps only partially transforming when there's less moonlight out, hence the full moon thing.
I was thinking the virus/bacteria/whatever (hereafter referred to as the v/b/w) maybe does something with the DNA or some such, and when transmitted, those features inherent to the original creature are then passed on to the next creature. I guess the cycle would probably stop there.
I'll admit that it's not very well thought out, and would be more believable as some nanomachine thing (which is saying something, plausibility wise) than a virus or what have you.