Airtight chamber hope for Rhys, 5

Rhys Harris loves rugby and adores his younger brother Morgan

A five-year-old boy from south Wales is to be sealed into a airtight hospital chamber for treatment to try to save him from a terminal illness.

Rhys Harris, from near Newbridge, has a rare genetic disease, Nemo, which is crippling his immune system and has left him dying from tuberculosis.

He will have chemotherapy before a bone marrow transplant in pioneering surgery at Newcastle General Hospital.

Rhys's father said the surgery was a "slim chance" but one they had to take.

The youngster is one of only six sufferers worldwide of the recently discovered condition.

The operation has not previously been carried out in the UK.

Only two people have had the treatment previously - one of whom survived.

Kevin and Dawn Harris are to move to Newcastle to be with their son during the treatment, without which they have been told he may live only another 18 months.

The flipside of the coin is not worth thinking about Father Kevin Harris

Mr Harris said: "We thought TB was something from the 1940s and 1950s. He went into hospital last August and we were informed it was terminal.

"It was just a question of when, not if, his body will collapse from the effects of the TB," he said.

"Our lives were turned upside down when we found that out."

Doctors are now screening for a bone marrow match - ideally from a donor who has had TB - and they plan to start Rhys's treatment soon.

Initially Rhys - who is severely hearing impaired after having meningitis as a baby - will remain inside a sterile ward, separated from the outside world by three airtight doors.

He will only be able to touch things placed on a red square surrounding his bed.

After four weeks, the sterilised area will be extended to a 12x12m square. Altogether, he could stay in isolation for nine months.

His parents will need to be scrubbed down and wear surgical masks and robes before visiting Rhys, while his younger brother Morgan, four, will have to stay in touch via a webcam.

Rhys has been deaf since a bout of meningitis as a baby

Mr Harris said: "It is difficult to tell him [Rhys] what is going on, but he takes it all in his stride.

"It is going to be a first, but these guys our amazing, We know it is a slim chance but we have to take it. The flipside of the coin is not worth thinking about.

Prof Andrew Cant, head of the bone marrow transplant unit at Newcastle General, said Rhys's operation has been performed successfully in the US, but never in the UK.

"His family have a very clear ideas of the risks involved but also the potential benefits for the rest of his life.

The professor said the only way to deal with Nemo was to knock out the body's immune system and replace it with one from a donated bone marrow.

"But there is a great risk when a child's immune system is removed and that is why he will need to be put into this highly-protective regime for several weeks," he said.

"He will be sealed off and a machine above the room will filter all the air while he is in there and everything possible is done to keep him away from infections in the outside world."