Questions about Velvet Disease

So I've had an outbreak of what I can only figure is velvet disease in my tank but I'm not sure about a couple things now that it seems to have run its course.

Basically how it happened was that I added a fish that appeared very healthy (and still does to this day) and a week or so afterward my other two fish started showing the typical signs of velvet and were dead within a couple days of the symptoms appearing. So here are the things I don't understand-

1) Can a fish be just a carrier of a disease like this and show no outward signs of having it? Like I said before, the fish that I added before this showed up in my tank is still alive a month later and has never appeared to be anything but completely healthy.

2) Given the answer to 1, how long should I be waiting and what precautions should I take before I can start to re-stock? I'd like to be able to treat the suspect fish in case it is carrying something, but in order to catch it I'm sure I'd have to pull everything out of my tank and I'd really like to avoid that if I can.

Thanks for any input.

*Edit* Whoops, just realized this should have gone in the disease forum. Mods, please move if desired...

I guess a 3rd question would be is it possible that the disease came in on coral and the fish that's still okay survived just by luck? I know I put some new frags in around the same time but don't remember exactly when...

Thanks for the help Amph. It does seem strange to me that a fish could just carry such an aggressive disease without being affected, but what do I know...

I guess I'm going to have to set up a hospital tank and try to figure out a way to catch this guy. Having another tank available is probably something I should have done a while ago anyway, I've never QT'd my new fish in the past and got away with it up to this point. Too bad it took something like this for me to learn my lesson.