David Tepper, founder and president of Appaloosa Management.

Cameron Costa | CNBC

Billionaire hedge fund manager David Tepper, who was bullish on the market just a few weeks ago, said the coronavirus outbreak has changed the environment around stocks.

Tepper, in an interview with Jim Cramer for TheStreet, said investors should be cautious until more is known about the virus.

“You have to be careful, because it may be a game changer. So you’ve just got to be cautious,” Tepper said.

Tepper had told CNBC two weeks ago that he thought the market would keep climbing, saying “I love riding a horse that’s running.”

Now, the coronavirus has “certainly ruined the environment” for stocks that was in place a few weeks ago, Tepper told Cramer.

The outbreak is still mostly impacting China, which has more than 17,000 confirmed cases and over 360 deaths. However, concerns about how the virus would dent global growth have hit markets around the globe, with major indexes in the United States falling by about 2% on Friday.

When asked by Cramer if long-term investors should stay in the market, Tepper indicated they should make sure they are not taking extra risks here.

“If you’re a long-term person, you better not be leveraged,” Tepper said.