The S&P 500 and the Dow Jones Industrial Average slid on Friday, hit by worries over the impact of the coronavirus epidemic on global growth, while strong earnings from Amazon.com checked losses on the Nasdaq.
Shares of the online retailer surged 9.2% after the company trumped Wall Street's estimates for holiday-quarter results, putting it back in the $1 trillion market capitalization club.
Gains in Amazon helped the consumer discretionary index rise 2.2%, while most other major indexes were in the red, with energy stocks tumbling 2.4%.
Wall Street indexes are on course to end the week on a poor note as virus fears continue to grip financial markets, although corporate earnings have been largely positive so far.
The World Health Organization declared the epidemic a global emergency on Thursday after the fast-spreading virus killed more than 200 people in China and infected thousands globally.
Disruptions in supply chains and travel curbs are expected to weigh on China's economy, prompting economists to temper their growth expectations for the world's second-largest economy.
"SARS experience suggests equities, especially in Asia, will keep falling until coronavirus infections stabilize and cyclical sectors are most vulnerable," Citi's global equity strategist Robert Buckland wrote in a note.
Citi, however, asked investors to "buy the dip". "Any further drop in global equities would make forecast returns more attractive," Buckland wrote.
Earlier, data showed the Chicago Purchasing Management index fell to a lower-than-expected 42.9 points in January, suggesting manufacturing activity in the Midwest contracted further.
At 10:03 a.m. ET, the Dow Jones Industrial Average was down 0.93%, at 28,591.30. The S&P 500 fell 0.65% to 3,262.41 and the Nasdaq Composite dropped 0.38% to 9,264.05.
Oil majors Exxon Mobil Corp and Chevron Corp dropped about 3% after disappointing results.
Visa Inc fell 2.7% as it fell short of analysts' estimate for first-quarter revenue and warned revenue would be crimped by incentives it provide to banking clients in 2020.
International Business Machines Corp gained 4.5% after naming a new chief executive officer.
Declining issues outnumbered advancers for a 2.49-to-1 ratio on the NYSE and a 2.80-to-1 ratio on the Nasdaq.
The S&P index recorded 29 new 52-week highs and 7 new lows, while the Nasdaq recorded 32 new highs and 50 new lows.