The Dow Jones Industrials fell more than 800 points and the S&P 500 as well as the Nasdaq hit three-week lows on Monday as a surge in coronavirus cases outside China fueled global growth worries and pushed investors to safer assets.

An increase in cases in Iran, Italy and South Korea over the weekend fanned fears of a pandemic, boosting gold prices and deepening the yield curve inversion between the 3-month and 10-year US. Treasury yields. An inversion of the curve is a classic recession signal.

All of the Dow's 30 blue-chip members and the 11 major S&P sectors were in the red. Leading the slide was a 3.4% drop in technology stocks. The defensive utilities and real estate indexes posted the smallest declines.

Apple Inc slid 4.1% as data showed sales of smartphones in China tumbled by more than a third in January.

Last week, Wall Street's main indexes notched record highs, partly on optimism that the global economy would be able to snap back after an initial hit, supported by central banks.

"It is not as though the numbers have changed dramatically but what has changed is the geography, which adds a new level of concern," said Art Hogan, chief market strategist at National Securities in New York.

"What the market is trying to predict here is how large will this get globally, and when will it start to peak." China-exposed chipmakers slipped with the Philadelphia SE Semiconductor index dropping 4%, while concerns about growing travel curbs dragged the NYSE Arca Airline Index down 6%.

The benchmark S&P 500 fell below its 50-day moving average and the blue-chip Dow slipped below its 100-day moving average, all closely watched indicators of momentum.

The CBOE Volatility Index, a gauge of investor anxiety, jumped to a six-month high.

The Dow Jones Industrial Average was down 815.31 points, or 2.81%, at 28,177.10, the S&P 500 was down 89.94 points, or 2.69%, at 3,247.81. The Nasdaq Composite was down 306.59 points, or 3.20%, at 9,270.01.

Health insurers such as UnitedHealth Group Inc and Cigna Corp dropped nearly 7% as Bernie Sanders, who backs the elimination of private health insurance, strengthened his position for the Democratic presidential nomination with a victory in the Nevada caucuses.

In a rare bright spot, Gilead Sciences Inc, whose antiviral remdesivir has shown promise in monkeys infected by a related coronavirus, rose 4.5%.

Declining issues outnumbered advancers for a 6.19-to-1 ratio on the NYSE and a 7.25-to-1 ratio on the Nasdaq.

The S&P index recorded seven new 52-week highs and 20 new lows, while the Nasdaq recorded 13 new highs and 125 new lows.