I'm sorry about your fish

If not thoroughly disinfecting the tank, you could get a new
activated carbon in your filter, and perform large and frequent water changes for a while. All this, perhaps, could help eradicate the disease. The important thing is to understand the virus/disease with which you're dealing. Every disease has a "life-span" and certain amount of time needs to pass, and the virus must be without an available host during that time, before the disease dies. So if you have no fish in your tank (or have a healthy fish that doesn't seem affected by the disease), get the new carbon, and perform large and frequent water changes for at least 2 weeks. Most viruses can live up to two weeks on their own in a tank (not being in a fish's body). I'd also keep the temperature increased at this time - higher temperatures kill viruses faster.
On the other hand, once your tank is empty, you could take everything out of the tank and clean it well, and get a new filter cartridge and cycle the tank again. There are different ways to clean a tank (some do it even with bleach), but I personally have always cleaned my tanks with warm/hot tap water and dried them in the sun.