Justin, fusarium is not a virus, but a fungus. This was all Oncidium Ring Spot Virus (ORSV) or Cymbidium Mosaic Virus (CymMV). Mostly CymMV, but there were a few OSRV positive and one or two that were positive for both! These are the two viruses that most often attack orchids and the two that tests are readily available for from Agdia and one other company. Viruses are easily spread by the sap (plant fluids) on hands or cutting tools that have not been properly disinfected (which takes some doing). Also when repotting, or from watering run off (according to Keith Davis in NC who usually has tested things through UNC, before he makes those types of proclamations.)
So, since a few of my virused plants were seedlings, it's most likely whatever plants I had that came in virused, I also did some spreading myself. Apparently, unless seed is propagated wet (by cutting into the pod to harvest the seeds) rather than dry harvesting the seed (when the pod bursts), seed propagating of plants should not spread virus. Since cattleyas and phals are cloned, viruses can be transferred that way also, the reason so few paphs and phrags are usually virused and none of mine were.
So now that I've tested everything, and certainly will continue to test any new plants that come in, I should be able to trust my collection will remain virus free. I will still disinfect clippers between each plant because other things (bacterial infections etc.) can be spread by using the same clippers on more than one plant without disinfecting.
I really thought I was being careful by disinfecting clippers with TSP (Tri-Sodium Phosphate) soak (mixed so concentrated it would precipitate out, for 10 min to overnight) as told to by the local orchid vendor between plants, but apparently that is not really effective, as I learned the hard way!
Now, I wear disposable nitrile gloves when I repot each plant and use a separate set of clippers while working on each plant, that then are disinfected by a 3 step process (rinse with soap and water, then Sodium Hydroxide/Virkon S, each 5-10 min) before being used again. I never re-use mix, pots or stakes, etc. This process was recommended by a large grower (with the science to back it up) who I believe is in CA, if I remember correctly. Sounds excessive, I'm sure to most, but I don't ever intend to take this kind of hit again, either financially or from a time standpoint.
Oh, to your question regarding seeing signs. In some cases there was color break on the flowers, an obvious sign of virus. In other, black/purple spotting on the leaves that at first I thought was from too much light, but it was suggested on this forum to be virus and I checked--it was! In some cases the plants had grown and flowered reasonably well several times, but the last flowering was unspectacular both in number and quality of blooms. In a few it was just failure to thrive, but in some cases, no signs had yet shown. So there you have it, hope this has been informative.