A surgeon says "nothing prepares you for this" as his daughter waits for a successful search for a blood stem cell donor who could save her life.
Arya Lloyd, 12, was diagnosed with the blood disorder aplastic anaemia.
Her parents, Geraint and Brundha Lloyd from Cambridge, have been told they are not suitable as donors.
Hospital doctor Mr Lloyd said: "I have spent half my life looking after people with serious medical problems, but nothing prepares you for this."
Aplastic anaemia is a life-threatening condition affecting the blood, where the bone marrow and stem cells do not produce enough blood cells.
Ordinarily the best match would be from a sibling, but as an only child, Arya's best hope now rests with a stranger who can offer a 100% match.
Mr Lloyd, a consultant general and colorectal surgeon at the Lister Hospital in Stevenage, Hertfordshire, was told his and his wife's stem cells could only offer a 50% match.
"Our world was turned on its head when we were given Arya's devastating diagnosis," he said.
"We're doing all we can to provide her with a second chance of life."
Blood cancer charity DKMS, which is searching globally for a match, reported a steep decline in new donors coming forward since March, due to Covid-19.
The challenge is particularly acute with Arya because she is of mixed heritage - half Indian and half Caucasian.
In the UK, patients from a black, Asian or other ethnic background have a 20% chance of finding the best possible donor match, compared to 69% of patients with north European backgrounds, DKMS said.
"We're at the mercy of others right now," said Mr Lloyd, who has family in India and the United States.
"We need their support."
DKMS said potential donors could join the UK stem cell registry by requesting one of its swab kits.