Thanks, Randy.  Also, today, this came in at honeybeeworld.com:

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After doing some further research, I was able to find this study: http://www.reeis.usda.gov/web/crisprojectpages/415067.html

This year, laboratory experiments in a small fumigation chamber (10 cubic ft) to determine the concentration of ozone needed to kill honey bee pests and pathogens. Tests were conducted using 1000 ppm for up to 3 days. Significant mortality was achieved for chalkbrood, but not for foulbrood. Wax moths infesting comb (all stages) were also found to be readily killed using 500 ppm of ozone. 
The pesticides coumophos and fluvalinate were significantly reduced by the ozone treatments, especially at high concentrations. It was difficult to reduce the pesticides to below 100 ppb. Elimination of pathogens from the comb was also evaluated. Chalkbrood in non-sporulating bee cadavers placed in the comb was completely eliminated, and the viability of the spores from cadavers was greatly decreased by the treatments. Methods to better quantify the actual spore mortality levels were developed as result, but experiments using these methods are still underway. Foulbrood scales were also placed in the comb, however, ozone had no measurable effect on the viability of this pathogen at the test concentrations used. 

While it doesn't appear to have much efficacy against foulbrood, one has to wonder if ozone would be effective against other viral transmissions via combs and boxes also since it is effective against chalk.

It is interesting to note the reduction of chemical buildup in the combs of checkmite and apistan. For beekeepers who are having fertility problems with drones and queens due to high levels of these chemicals in the combs, this may be a way of cleaning up old combs.

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http://www.honeybeeworld.com/forum/viewtopic.php?f=8&t=223&sid=9a8d83318856e57fe5b0975ae80caf4e&p=763#p763

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