It marks the second time that Chagaev has pulled out of a defence claiming illness.

The Uzbekistan native was set to face then-title holder Sultan Ibragimov eight months ago but withdrew with what was described as "acute inflammation of the body".

Chagaev’s latest illness was described by his physician, Dr Michael Ehnert, in a statement released by Universum-Box Promotion on Tuesday.

"Ruslan Chagaev suffers from a protracted virus infection," the statement read.

"In medical terms it’s a viral laryngitis and pharyngitis. For non-doctors, it’s a highly feverish viral infection of the upper respiratory tract with heavy symptoms.

"The medical treatment makes it absolutely necessary that he stop training."

Chagaev (24-0-1, 17 KOs) did return from his last illness to win a lopsided unanimous decision over Englishman Matt Skelton on January 19.

In April 2007, the 29-year-old Chagaev won the WBA strap with a majority decision over the 7-foot, 320-pound Valuev.

Valuev (48-1, 34 KOs) earned a rematch against Chagaev by winning a unanimous decision over Sergei Liakhovich on February 16 in a WBA elimination bout.

It is now uncertain when Chagaev will meet the Russian giant.