Quote Originally Posted by Luna Guardian View Post
If we close out the possibility of a virus, and utterly ridiculous ideas such as aliens or divine (Infernal?) intervention, I think a few good options might be nano-machines or parasites.

The former would allow for the "mutations" we've seen with some degree of scientific accuracy and would allow the "infection" to work through the machines multiplying in a host body. The machines could embed themselves in all tissue, or at least bodily fluids such as blood and saliva, and transfer from one carrier to another. This might also give an explanation to the "smart ones" and the coordination we've seen, since the smart ones may have more advanced machines or may employ or control them to a higher degree and through a kind of wireless network send messages to the nanites in other infected.

The parasite theory works in a similar fashion, but the mutations might be more difficult to explain. Ideas?
There's always the possibility of more than one system at work or more than one wave of intervention working together. Like, you could have multiple infections of a virus each carrying a piece of the puzzle or mutation. Then, maybe nano machines providing some sort of advantage to some.

The problem with divine or infernal causes (looking at it from a purely what works in fiction perspective) is it's so intellectually and emotionally fraught it takes people out of the story. I guess, basically, it couldn't be something that a lot of people have discounted in their daily lives.

The problem with nano technology is it's a bit like the a lot of the future we've been promised. The reality right now is more "look how teeny tiny I made that chemical" rather than true machines. But that's true of just about any scientific explanation. Unless,...you could have something developed for a benign purpose being twisted.