George Michael's singing voice could be badly affected by his current illness.

The British singer is being treated for pneumonia in Vienna, Austria, after falling ill last week. He's spent time in intensive care and is reported to have developed another life-threatening respiratory condition which stops oxygen getting into the blood.

George is being treated in a special bed to help his breathing and ear, nose and throat surgeon Gerrit Wohlt has warned his road to recovery will be long.

"In the worst case scenario, being on a ventilator could harm his vocal cords. He could end up with a hoarse voice, so a new year comeback is unlikely. He will need months of rest," he told British newspaper The Daily Mirror.

The 48-year-old singer's boyfriend Fadi Fawaz has been with him every day since he fell ill. Over the weekend Fadi insisted the star is improving and responding to treatment.

George's father Kyriacos Panayiotou and sisters Melanie and Yioda have also been keeping a bedside vigil for the star, and his ex-partner Kenny Goss is en route to Austria at the moment.

"His whole family are with him. They are very close-knit," a source told British newspaper The Daily Mail. "George is just such a lucky man in that sense. He's so adored."

George and Kenny split in 2009 although the singer only confirmed the news this year. They had been together for 13 years.

"Kenny of course is very concerned. He has been in touch every day. They will always be the best of friends," the Daily Mail insider added.

George has been forced to postpone the rest of his Symphonica world tour due to his illness.