Humans were so judgmental. They used outward appearances to justify the way they treated those around them, which disgusted the gods. Didn't they realize there was more to the world than just its physical form? Therefore, the gods decided to take action.
The virus would make physical appearances obsolete. Well, technically not obsolete, because humans would be able to change into whatever they desired, from an animal to a plant to the ugliest or most beautiful human alive, but none of those forms would be permanent. As part of the gods' judgment, a human would not be able to maintain their current form longer than 24 hours, at which point they must shift to the point where their physical structure changed completely. They could stay human, but they would have to change their form greatly in terms of age and gender, and even to the point of little things such as hair and eye color. Furthermore, they could not return to a form they had used before for at least a week.
Given the amount of effort to stay a human, it would make more sense to change into different creatures. Even mythological creatures were not out of bounds, although there would be size limits. Becoming something much larger than a horse or smaller than a housecat would take concentration and hard work, and would reduce the time before the next shift accordingly.
Should a human fail to actively shift when time was up, the human would involuntarily ooze into an amorphous blob. There would be no harm done, but the human would be incapable of eating, talking, etc. in this form, which limited the amount of time they could spend without shifting. Once a shift was begun, the clock would begin to tick down again.
Those who bore the judgment and were insulted by others regarding their appearance would involuntarily exude a pheromone which would spread the judgment, causing those inflicting the insults to suffer the judgment next. Eventually, the judgment of the gods would spread over the entire world. By that point, the world would find it hard to figure out how it had begun.
But the gods would know, because they had chosen someone in particular to be the first bearer of their judgment, or perhaps in this case, gift. That person was...