One of David Einhorn's big shorts is surging

Athenahealth, which is one of hedge fund manager David Einhorn's short targets, is surging after the company beat third-quarter earnings estimates on Thursday.

The stock was last up 24%, or about $30.92, at $159.01 per share.

Einhorn revealed he was betting against the company in 2014.

On May 5, 2014, he revealed his position at the Sohn Conference. The stock's closing price that day was $126.78. At the time, Einhorn said that he thought the stock could fall 80%.

Athenahealth, which is led by Jonathan Bush, is a business that provides outsourced administrative services for healthcare providers. Bush has declared that he's "absolutely confident" Athenahealth is a "$1,000 stock."

Greenlight Capital has fallen 17.1% for the year through the end of September, according the fund's third quarter report.

Einhorn launched Greenlight Capital in May 1996 with $900,000 from friends and family. Einhorn became known for a call he made in spring 2008 to short Lehman Brothers.

He's currently on track for his second-losing year ever. His only previous down year was in 2008, when his fund lost 23%.

Here's a five day chart: