The Doc stopped in his tracks and slapped his forehead. He would not be affected by the virus unless he turned the dormant gene he manipulated to keep the virus from continually changing the person back off.
The Doc used to be a 50 something man, until he tested the non-contagious version on himself. Minutes later he was 10 years old injecting himself with the gene reverser and then the virus again. Luckily he didn't have to keep trying, his body aged to just around 20.
Making his way back to the front door he could hear sniffling. A child, no older than 7 now stood in his doorway, drowning in a shirt, the rest of his clothes around his ankles.
"Hey Mister, what happened? Are you my daddy?" the boy asked.