SAN FRANCISCO (Reuters) - The S&P 500 suffered its worst day in two years on Monday as a surge in coronavirus cases outside China rattled investors already worried about valuations following recent record highs.

FILE PHOTO: The New York Stock Exchange building is seen from Broad Street in Lower Manhattan in New York, January 20, 2016. REUTERS/Mike Segar

The S&P 500’s 3.35% slump was the leading U.S. stock index’s deepest one-day loss since February 2018, when Wall Street was in a correction.

The fear in Monday’s session came after investors in recent months often downplayed the overall risk related to the new coronavirus. Monday’s drop wiped out all of the S&P 500’s gains for 2020.

“With stock prices and valuations still near cycle highs, the risk of a worsening virus outbreak has not been priced into the market to a great extent,” Truist/SunTrust Advisory Chief Market Strategist Keith Lerner wrote in a client note.

S&P 500 sector indexes are mostly still close to their record highs, with the exception of energy .SPNY. The S&P information technology index .SPLRCT tumbled 4.2% on Monday, slammed by losses for chipmakers and Apple AAPL.O, which rely more than most other U.S. companies on China. The information technology index is down over 7% from its record high on Feb 19, but remains up almost 4% in 2020.

(GRAPHIC: Sectors vs 52-week highs - )

The Philadelphia Semiconductor Index .SOX has fallen 9% from its record high last week.

(GRAPHIC: Philadelphia Semiconductor Index - )

Increased fears that the coronavirus could become a pandemic led to a spike in the number of listings on the New York Stock Exchange hitting 52-week lows. At 503, Monday saw the greatest number of new lows in a session since last August. At the same time, the number of stocks hitting 52-week highs shrank to 278 from over 400 on Friday.

(GRAPHIC: New highs and lows - )