Rather than risk it, I would discard the gravel at least (it's cheap, especially if you use pool filter sand like I do).
To disinfect the tank, I would add a "large" quantity of bleach (make sure it's unscented) and fill the tank with water. Go ahead and run the filter on the aquarium with no media to make sure everything is dead in the filter as well. You could also place the heater, large rocks, etc. in there also. After it has been circulating for 30 minutes to an hour, drain it, then rinse with water and let it sun dry. For large rocks, rinse several times and then when they no longer smell like bleach, soak them in a bucket and add a bunch of dechlorinator. Leave them in there for a while and then air dry them as well.
If you have driftwood, a method I have heard mentioned, but never tried myself, is to run it in the dishwasher (with no detergent, of course).
That should take care of any pathogens that are present.