The mother of a two-year-old boy who is living with a new heart says fears he may catch Covid-19 have pushed family stress levels "through the roof".
Benjamin Rayner, from Peterborough, underwent a successful transplant operation in April 2018, aged eight months.
Routine hospital appointments are now on hold while the family shield him during lockdown.
His mother, Ashley Hardy, said: "I don't want my son exposed to any risk."
Benjamin, now a "confident and happy" 28-month-old, was born with the congenital hypoplastic left heart syndrome and spent the first months of his life in the high-dependency unit of Newcastle's Freeman Hospital.
The disease, caused when the heart fails to develop properly, affects the organ's ability to pump oxygen.
Benjamin's parents took it in turns to travel 200 miles (326km) from Cambridgeshire every week to stay by his side.
By Christmas 2017, he had undergone two open heart operations - before a new heart was found in April 2018.
He suffered complications and a stroke in December 2018 but has gone on to lead a normal life.
"The elderly, people who have health issues of any age, and babies like Benjamin, are at a high risk; this virus could be fatal," Ms Hardy said.
"The stress and anxiety of the 'what-ifs' with coronavirus are through the roof at the moment. We are so scared he'll get it.
"Please listen to the guidelines and stay at home."
Benjamin will be on anti-rejection medication and immuno-suppressants for life, she said.
Hospital appointments every six weeks in Newcastle have been put on hold while pandemic restrictions continue.
She said Benjamin "loves to be the centre of attention" and "takes everything in his stride", despite his dramatic early months.
He is living with his father, Ms Hardy's former partner David, while she prepares to begin a new job in a care home.
"We are taking every precaution, but he is a fighter - he's stubborn, like me," she said.
NHS Blood and Transplant (NHSBT), which runs the UK's organ transplant network, warned the coronavirus outbreak was putting pressure on the service.
The number of transplants since March has fallen dramatically - compared to 80 a week a year ago.
As of 22 April, 287 post-transplant patients across the UK had contracted coronavirus, according to the NHSBT.
Ms Hardy - who also has two daughters, aged 11 and eight - said she thought of Benjamin's heart donor every day.
"That poor family gave my son a chance to live. Some day I want them to hear their loved one's heart beat in my son," she said.
"There are no words, even today."