It's hard to diagnose the fungus unless the frog is on its last legs. The frog becomes lethargic and goes off food, loses weight and eventually dies without a very apparent cause, but this can describe almost any amphibian disease.

The fact is that most amphibians in the pet trade have been exposed to it and the vast majority don't succumb to it and die. There are some well-meaning hobbyists who think that by treating one frog that it will never be exposed again - in my opinion this is unrealistic unless you never acquire another frog and don't come into contact with amphibians again.