Bessie Really interesting article. Always a bit frustrating to get just the abstract. I will see if I can get the full text, though it might have to be through Dr Pappu. I did read through the citations at the link, which added some more detail. The abstract and many of the citations refer to "environmental waters and waters used for irrigation and in hydroponic systems", so I think it is not just hydroponic situations they are covering. Some of the citations quoted refer to some virus families which appear to be more easily transmitted via water than others. Some viruses are more stable outside of their host than others (they can't reproduce outside the host, but they can be transmitted). Tobacco Mosaic Virus is usually cited as the most stable (note that this is NOT the same as the Tobacco Streak Virus which is one of the viruses tested for at the WSU labs). Evidently there is confirmation that at least some of the more stable viruses can be transmitted through water. But it sounds like there are many more which probably don't. I don't know how stable the viruses are that WSU is testing for, just that they are not as bad as TMV.
I would like to see more detail on virus presence in the water vs how successful that virus is in actually infecting plants it contacts. My thought would be that the longer contaminated water was in contact with the roots, the greater the chance of infection. Flowing water in large volumes would be the least likely, smaller amounts that stay in contact with the roots longer would be more likely. If the roots are allowed to grow together, in direct contact, this would add another method of transfer.
Personally, I am not comfortable with the oasis method, where the cuttings are all touching and sharing the same water. I don't know how likely it would be to spread virus, but it seems a possibility. I do know that bacterial and fungal diseases could spread easily that way. I think spread through the air is much less likely, since virus particles cannot move on their own from plant to plant, they have to be carried.
