A five-month-old boy died after contracting a virus from another child on a hospital ward, an inquest heard.
Noe Tomsett caught the virus while on the paediatric intensive care unit at St George's Hospital in Tooting, south London.
The baby from Morden, south London, died on 21 March 2010.
Adenoviral pneumonia was given as the cause of death, but exomphalos and bronchomalacia were also listed as factors.
Deputy Westminster Coroner Dr Shirley Radcliffe told Noe's parents: "At the end of the day, your baby has died, and your baby acquired an infection on the ward.
"That must be devastating for you to deal with."
She added: "We have heard today that your baby received excellent care while he was on the intensive care unit, and it was a tragedy that he acquired the adenovirus on the unit.
"But we can understand how these things can happen, with the best will in the world. "
The hearing was told that Noe was born by emergency caesarean section to Nicole Deutsch and Brett Tomsett, of Morden, on 22 September 2009.
Consultant paediatrician Dr Martin Grey said doctors were concerned that Noe had acquired the virus on the ward and asked the medical directors to investigate potential cross-infection.
"Given that the patient next door had adenovirus, that may have been the source of the infection," he said.
"We can hypothesise that is the most probable solution, but we can't prove it."
After the hearing, Noe's father said: "I think there was long-term failure in their care of Noe. The general approach of the hospital was chaotic and disorganised."
A statement from St George's Hospital said: "Our sympathies go to the family at this difficult time.
"In delivering a verdict of death by natural causes the coroner said that Noe Tomsett had received excellent care in St George's paediatric intensive care unit."