What would happen if they did get hit by it, I don’t think there’s a storyline/run where Superman or any krptonians get sick (correct me if I am wrong)or have any virus that almost wipe them out unless If you exclude non-canon material. But to make it more interesting there are the scenarios.
1.they live in krpton but next to a red star
2.they live in krpton but next to a yellow star
3.they live in krpton but next to a white star
4. they live in krpton but next to a blue star