Bates, Swan and Chiaramonte fulfill exactly what the cover of Action 496 (June 1979) proclaims. Superman brings a plague from Kandor to Earth, endangering everyone on the planet.
For the first time we see that he does take precautions, sterilizing his body when he emerges from Kandor. But it just wasn’t enough this time.
Superman tries to seek out help to find a cure, or a solution. But when he approaches the JLA satellite is vanishes, and the same thing happens to Supergirl when he seeks her out.
The Kandorians are actually behind these illusions. When they informed Superman about the infection, they also shot an antidote into him. He emits it, without being aware, and the more stress he is under, the more he gives off, curing himself, and everyone else. Kind of manipulative of them.