UnitedHealth jumps after Warren Buffett bets big on insurer

** Shares of health insurer UnitedHealth UNH.N rise ~14% to $309.51

** Stock set for its biggest one-day pct gain since October 2008, if gains hold

** Late on Thursday, Warren Buffett's Berkshire Hathaway BRKa.N acquired 5 million shares in UNH, according to a regulatory filing

** Berkshire owned 5.04 million UnitedHealth shares worth about $1.57 billion, as of June 30

** "While UnitedHealth still faces elevated uncertainty, it is good to see that this renowned investment firm also believes the market is discounting assumptions that are too pessimistic for the long term, which is similar to our view," said Morningstar analyst Julie Utterback

** Shares of other insurers also rise with Centene CNC.N up 5.1%, Molina Healthcare MOH.N up 3.8%, Elevance Health ELV.N up 3.6%, Humana HUM.N up 2.2% and Cigna CI.N up 1.5%

** As of last close, UNH down 46.3%, ELV down 19.9%, MOH down 45.2%, CNC down 55.6%, while CI up 5.2% and HUM up 10.9% YTD