Ian Thorpe may lose the use of an arm after he contracted a bug following surgery while at home in Switzerland.
The 31-year-old has returned to his hometown of Sydney, where he is intensive care, following surgery at a hospital in the Swiss town of Ronco sopra Ascona.
Network Seven reported on Tuesday evening the five-time Olympic gold medallist contracted the bug after surgery at the hospital.
Friends are fearful his condition is so serious he may lose the use of his left arm.
In his autobiography, published last year, Thorpe said "not even my family is aware that I've spent a lot of my life battling what I can only describe as crippling depression."
The Aussie was a popular pundit during the BBC's coverage of the London 2012 Olympics.