Jack watched them. There was nothing to do--going out of the Hub for a doctor would unleash the worst plague of the fourth millennium on defenseless Cardiff.
Now that they were all unconscious, Jack allowed himself some favoritism, staying at Ianto's side, watching his skin fade to gray as his rattling breaths slowed. When a golden aura appeared around his face, Jack thought he was infected after all, hallucinating.
Within seconds he recognized a regeneration. At the end of the light show, Ianto blinked new green eyes, looked around, and said, "Jack, help me up, I can fix this."