Because salt is very strongly antimicrobial, I hypothesize that soaking seeds in a strong salt water solution might be enough to disinfect them of diseases that are not inside the seeds. This could potentially be more effective than bleach when it comes to fungus.
I don't think this would harm the seeds of many vegetables, considering a study I read about where the conductor of the study was interested in determining whether vegetable seeds could survive crossing the ocean. The seeds tended to sprout after soaking for a month or so in a certain solution. For my hypothesis, I think an hour-long soak might be sufficient, however (but I would probably want a saltier solution).
Location: SW Idaho, USA
USDA hardiness zone: 6
Elevation: 2,260 feet Profile post