Shares of UnitedHealth Group are surging before the market open Friday as Warren Buffett’s Berkshire Hathaway disclosed that it recently purchased shares of the beleaguered insurer.

UnitedHealth Group shares popped Friday after Berkshire Hathaway announced it purchased 5 million shares of the insurance giant.

UnitedHealth Group ( UNH 12.04%) has been a solid dividend growth stock for years. Generally, its yield has been fairly low, due to the stock's rising value. Even as the healthcare insurance giant has grown its dividend, its yield hasn't been particularly high or noteworthy.

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UNH stock soared after Warren Buffett’s Berkshire Hathaway revealed it bought shares of the healthcare company. Nonetheless, UnitedHealth faces a long list of unresolved issues.

Year to date, the stock has fallen by nearly 45%, which is by no means normal for the healthcare stock. In fact, this is the worst it has performed since the Great Recession, when it tumbled by more than 54% in 2008.

UnitedHealth Group's public reputation is still reeling, yet its battered stock has been something that more and more investors can't seem to resist. Why it matters: Recent interest in its stock, from everyday investors to Wall Street's titans,

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