Australian boxing legend Jeff Fenech is battling a “mystery infection” that has left him in intensive care in a Sydney hospital.

Hall of Famer Fenech was rushed to hospital on Tuesday with a body temperature of nearly 40, amid fears he has a concerning heart issue.

“I feel s—house,” Fenech told News Corp.

“I’m as sick as a dog. I have a mystery infection. I’m sick of it.

“They think it has something to do with my heart and valves. They have done heaps of tests. I don’t yet know what the results are.”

Fenech, 59, also reportedly has a swollen wrist.

In 2019, the boxing legend had five hours of heart surgery in Thailand to replace an infected valve. Doctors are also examining that and adjoining valves.

At the time, it was revealed Fenech had been coughing up blood and had a shaking fit before being admitted to hospital. Daughter Kayla said at the time that the surgery came after he ignored days of discomfort, unaware how serious his ill health was.

“We landed and literally rushed to the hospital and got there, thank God, he was feeling OK, I guess he was scared. It was good to speak to him and give him a hug before he went in,” she told the Nine Network.

On Wednesday, Fenech told News Corp he had been battling a fever for nearly a fortnight, with his temperature reaching as high as 39.8 degrees.

“I hope I don’t need surgery but I don’t know. I hope not, I hope not,” he said.

“I also have a really bad infection in my wrist and they think it could be heart related. If you see my wrist you’d die, it’s massive. It’s red, inflamed, swollen and sore.

“It could be an infection coming from the valves which has spread through my body. They don’t know yet.

“Of course I’m worried, of course I am. I don’t want another operation. F—k that.”

In his 33-fight professional boxing career, Fenech won 29 bouts, including 21 knockouts, represented Australia at the 1984 Olympic Games and was a world champion in three weight divisions.

He won the final fight of his career – a majority decision win over Azumah Nelson – in 2008.