“The doctor called me yesterday to inform me that on Sunday Willie went into respiratory failure and he is now in an induced coma and mechanical ventilation," said Ms O'Neill.
“They are treating him with 3 different antibiotics for 3 types of infections, which appear to be consuming him at this time.
“We are all hoping that the treatments the hospital are giving him while in this induced coma will help to improve his overall condition and at some point enable him to breath on his own and be brought out of this coma.
“Understandably this situation is very difficult and very sad for everyone involved.
Snooker legend Willie Thorne at the Crucible
Image credit: Imago
“A lot of prayer and a lot of positive energy is needed for this current situation.
"Once again I thank everybody for your messages of support and words of encouragement, I know they have been a comfort to Willie but also for me too.
"Hopefully soon I can update you with something more positive."
It was reported in late May that the former world number seven had been unable to move his arms to answer phone calls at his rented home in the Spanish city of Alicante amid fears he could also be fighting the blood poisoning illness of sepsis during his cancer battle.
The 1985 Mercantile Credit Classic winner was taken to hospital on 2 May. He has since undergone three blood transfusions, and treatment for a virus amid the global coronavirus outbreak.