UnitedHealth shares soared after Warren Buffett revealed a stake of 5 million shares, worth about $1.6 billion, in the troubled health insurer. The "Big Short" investor Michael Burry and Appaloosa Management's David Tepper also disclosed sizable stakes in the company.

Shares of UnitedHealth Group surged more than 13% on Friday after billionaire Warren Buffett's Berkshire Hathaway bought 5 million shares of the company, providing a shot in the arm for investors who think the health conglomerate will turn around under its new CEO.

UnitedHealth shares jumped 10 per cent in pre-market trading on Friday after Warren Buffett’s Berkshire Hathaway snapped up a stake in the troubled US healthcare group. The new investment, worth $1.6bn at the end of June, was disclosed in a filing late on Thursday detailing changes to Berkshire’s $268bn stock portfolio during the second quarter.