When exposed on the highest setting of an 800 watt microwave oven, a dry, cellulose
sponge was disinfected after 30 seconds. A wet sponge was disinfected after 60 seconds.
I can't vouch for disease prevention, but I am positive this makes the sponges last longer. We were going through sponges at a great pace -- due to their tendency to develop an ... errr ... odor (note to our few guests -- we use a dishwasher for your dishes). Zapping the sponge every few days now gives it a reasonable lifespan.