A baby from Greater Manchester who was seriously ill with swine flu returned home for Christmas.
Harvey Flanagan, now aged six weeks, was "fighting for his life" at the Royal Manchester Children's Hospital before Christmas, his parents said.
Andrew Flanagan and Michelle Dyer, claim Stockport's Stepping Hill Hospital twice failed to identify swine flu. It said it would investigate.
Ms Dyer, of Stockport, said her son's return home was "amazing".
"Last week he was on death's door, his body was shutting down."
Mr Flanagan added: "He was fighting for his life. He was hypothermic, his blood pressure was extremely low, he didn't respond to touches or movement or an injection in his leg."