U.S. stocks endured their worst drop since 2008 on Monday as a free fall in oil prices and mounting coronavirus cases frightened investors and pushed major indexes to the edge of a bear market.

The heavy selling began in Asian markets late Sunday, spread throughout Europe on Monday and sent prices plunging on everything from bank stocks and oil futures to U.S. Treasurys.

Monday's rout added to recent losses and left the broader stock market down nearly 20% – almost bear territory – from its high in mid-February.

The Dow Jones Industrial Average dropped 2,013.76 points, or 7.8%, to close at 23,851.02 on Monday – its worst one-day percentage drop since October 2008. That left the blue-chip average down 19% from its all-time high just three weeks ago. The Standard & Poor’s 500 fell 225.81 points, or 7.6%, to end at 2,746.56, its biggest one-day percentage decline since December 2008. The broad index, which is used as a benchmark for mutual funds, was off 19% from its record high Feb. 19.

The Nasdaq Composite dropped 624.94 points, or 7.3%, to finish at 7,950.68, putting the technology-heavy index 19% below last month's record.

Sparking the sell-off was a weekend rift between major oil producers Russia and Saudi Arabia over how to prop up crude prices. That set off an alarming slide in oil prices late Sunday, rattling investors who already worried that the spreading coronavirus could grind the global economy to a halt.

"We're seeing borderline panic because of fear," says R.J. Grant, director of equity trading at investment bank KBW. "Uncertainty is what's causing all of this. We know there's going to be an economic impact, but we just don't know how big. Until we get clarity, people aren't going to come back into the stock market, that's for sure."

Stocks have gyrated in recent weeks after uncertainty over how much damage the virus would do to the global economy. The worldwide total of cases surpassed 111,000 on Monday, with confirmed U.S. cases exceeding 600. The worldwide death toll approached 4,000 and rose to 26 in the U.S.

Economists were concerned that disruptions to supply chains and corporate profits will restrain U.S. growth. Anxieties over the possible damage to the economy have wiped out $5.3 trillion in stock value and raised fears of a recession.

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"Demand is slowing. People aren't taking trips. They're not taking cruises. They're not going on vacations," says Adam Sarhan, CEO at 50 Park Investments. "That means money isn't being spent on airlines, hotels or conference halls. If you don't have people moving within the economy, growth comes to a grinding halt."

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Monday's sharp drop nearly ended the longest-ever bull market on the very day it turned 11. The bull market began on March 9, 2009, when stocks bottomed during the global financial crisis. The S&P 500 has risen more than 300% since then.

If an investor had put $10,000 in an S&P 500 index fund on March 9, 2009, it would have been worth $62,888 with dividends when the stock market hit a record on Feb. 19 and would be worth $51,059 through Monday's close.

To be sure, the U.S. economy is strong. The unemployment rate is at a half-century low, consumer spending has remained robust and the housing market has firmed.

“I’ve never seen anything like this,” says John Spensieri, head of U.S. equities trading at Stifel. “But the U.S. economy was still humming along pretty well before this happened. Once there’s a clearer vision on when this virus could be contained, the pendulum could shift and provide a buying opportunity for investors.”

Investors are looking ahead to next week’s Federal Reserve meeting for further clarity on the outlook for the economy. Fed officials surprised markets last week and cut interest rates in a rare emergency move.

Federal funds futures, which traders use to bet on the path of central bank policy, showed Monday that investors were betting there was a 75% chance the Fed will cut interest rates by 75 basis points at its March 17-18 meeting, according to CME Group data. That would lower rates to historic lows near zero.

"The Fed cutting rates more will help the economy in some ways, but it still won't be the only remedy to thwart people's fears," Spensieri says.

Goldman Sachs forecasts the virus risks will be relatively short-lived for financial markets, with the S&P 500 projected to end the year at 3,400, or up 14%. If the contagion lasts for an extended period of time, however, the U.S. economy could slip into a recession and the broad index could fall to 2,450, or a drop of 18% for the year, Goldman analysts project.

Along with stocks, bond yields also slid with investors flocking to safer corners of the market. The 10-year Treasury yield, which falls when investors are worried about a weaker economy and buy bonds, resumed its decline, briefly dipping to 0.318%. The benchmark is used as a barometer for mortgage rates and auto loans.

Crude prices also plunged 24%, their worst loss since the Gulf War in 1991.

While low oil prices can eventually translate into cheaper gasoline, they are wreaking havoc on already struggling energy companies and countries that depend on oil, including the No. 1 producer, the United States.

West Texas Intermediate, the U.S. benchmark for crude oil, slid 24.6% to settle at $31.13 a barrel, its worst day since January 1991. Brent crude, the international benchmark, dropped 24.1% to $34.36 a barrel, also its worst day since 1991.

In Europe, London’s FTSE 100 sank 7.7% and Frankfurt’s DAX tumbled 7.9%. France’s CAC 40 lost 8.4%.

Asian stock markets plummeted overnight. Japan's Nikkei 225 slid 5.1% while Australia's S&P/ASX 200 shed 7.3%. Hong Kong's Hang Seng index lost 4.2%.

Contributing The Associated Press