Stocks hit a new coronavirus crisis low Wednesday as investors worried governmental response to the pandemic wouldn't be sufficient. A key market-wide circuit breaker was triggered for the second time in just three days as volatility continued to roil Wall Street. Here's what happened:

5:31 pm: NYSE to temporarily close floor, move to electronic trading after positive coronavirus tests

The New York Stock Exchange said Wednesday it will temporarily close its historic trading floor and move fully to electronic trading after two people tested positive for coronavirus infection at screenings it had set up this week. All-electronic trading will begin on March 23 at the open, the exchange said. The closure was in part as a result of positive coronavirus tests of two people, Stacey Cunningham, President of the NYSE, told CNBC. The entrants were stopped at the medical screenings at the Big Board. - Li

4:30 pm: Sell-off by the numbers

Dow closed down 6.3% after hitting a low of 18,917.46 its lowest level since Nov. 21, 2016

This month: Dow is down 21.69% on pace for its worst month since Oct. 1987 when the Dow lost 23.22%

This year: Dow is down 30.27% on pace for its worst year since 2008 when the Dow lost 33.84%

Dow is 32.7% below its intraday all-time high of 29,568.57 from Feb. 12 S&P closed down 5.17% hitting a low today of 2,280.52 its lowest level since Feb. 2, 2017

This month: S&P is down 18.81% on pace for its worst month since Oct. 1987 when the S&P lost 21.76%

This year: S&P is down 25.76% on pace for its worst year since 2008 when the S&P lost 38.49%

S&P is 29.32% below its intraday all-time high of 3,393.52 from Feb. 19 Sectors: 11 out of 11 sectors were negative Wednesday led by Energy down 14.24% — Francolla

4:15 pm: Sentiment indicators don't matter now, Josh Brown says

The fear about the coronavirus makes traditional measures of investor attitudes less relevant, Ritholtz Wealth Management CEO Josh Brown said after Wednesday's sell-off. "I don't think sentiment matters anymore. I think all those Investors Intelligence surveys — you can throw them out," Brown said on "Closing Bell," adding that investors were more focused on health issues and other aspects of the pandemic. "A lot of the moves we're seeing are based on people taking money out of the market that they think they're going to need to live on," Brown said. He added that news about successful treatments of the coronavirus could help the market bounce back. — Pound

4:09 pm: Six Dow stocks close in the green

Amid Wednesday's violent market dive, six stocks in the Dow Jones Industrial Average ended the day in positive territory. Walgreens Boots Alliance closed up 6.5%, Cisco Systems rose 5.2%, Walmart jumped 2.8% and 3M popped 1.9%. Pfizer and Verizon both ended the day up less than 1%. – Fitzgerald

4:01 pm: Dow closes down 1,300 points

The stock market tumbled again as investors grew increasingly concerned about the economic fallout from the coronavirus. The Dow closed the session more than 1,300 points lower, after plunging as much as 2,319 points at its session low. The S&P 500 dropped 5.1% and the Nasdaq Composite was down 4.7%. The massive sell-off tripped a trading halt in afternoon trading, the second time in three days. — Li

3:15 pm: Final hour of trading: Stocks head for big losses again

With less than one hour to go, the major averages were headed for another steep decline amid concerns over the economic destruction from the coronavirus. The Dow was down more than 1,600 points, or 7.7%. The S&P 500 and Nasdaq were down more than 6% each. The major averages were all down more than 8% earlier in the day. —Imbert

3:09 pm: Stifel CEO calls for immediate stimulus, says 'the market needs some certainty'

Congressional leaders and the Trump administration need to push through a fiscal stimulus deal immediately and not fight over details, Ronald Kruszewski, the chairman and CEO of Stifel said on "Power Lunch." "We need the fiscal stimulus. I don't care what the heck the plan is at some point. Get one announced. Whether it's $1,000, $2,000, bailouts, whatever. The market needs some certainty and some action," Kruszewski said."That's a message to Washington. Why we don't have a fiscal deal done because there's some political partisanship is ridiculous. This needs to be announced today," he added. —Pound

2:42 pm: Bill Miller calls this market one of the best buying opportunities of his lifetime

Investor Bill Miller said during Wednesday's violent market dive that the current climate is one of the best buying opportunities of his lifetime. "I think this is an exceptional buying opportunity," Miller said on CNBC's "The Exchange" on Wednesday. As Miller was speaking, trading was halted because the S&P 500 fell more than 7%, triggering the level 1 "circuit breaker." - Fitzgerald

1:51 pm: Dow's historic fall

1:49 pm: Decliners lead advancers 30 to 1

More than 30 stocks traded lower at the New York Stock Exchange on Wednesday for every advancing stock as the coronavirus crisis sell-off reached a new low. In total, more than 2,900 stocks were down at the NYSE while 95 traded higher. —Imbert

1:34 pm: Stocks plunge to session low with Dow down more than 2,000 points

Stock losses accelerated in afternoon trading with the Dow dropping 2,128 points for a 10% loss. The S&P 500 dropped 9%, while the Nasdaq was down 8.3%. - Stevens

1:14 pm: Stocks resume trading

After a 15-minute halt, stocks are trading again. The Dow is down 1,753 points, or 8.3%, while the S&P 500 and Nasdaq are down 7.3% and 6.7%, respectively. - Stevens

1:04 pm: Bill Ackman pleads to Trump to increase closures to save the economy: 'Shut it down now'

Longtime hedge fund manager Bill Ackman urged President Donald Trump to shut down the country for 30 days to contain the coronavirus, calling it the only option to rescue the economy. "What's scaring the American people and corporate America now is the gradual roll-out," Ackman said on CNBC's "Halftime Report" on Wednesday. "We need to shut it down now... This is the only answer.""If he can save the country from the coronavirus, he will get re-elected," Ackman said. - Li

12:56 pm: Trading halted as S&P 500 drops 7%

Stocks are halted for trading after the S&P 500 dropped 7%, kicking in the level one "circuit breaker." - Stevens

12:30 pm: Natural gas prices fall to lowest level in more than 24 years

Natural gas is down 7% today, and is now trading at its lowest level since Sept. 20, 1995. - Francolla, Stevens

11:50 am: Markets at midday: Stocks tumble once again as volatility reigns supreme

Around midday, the major averages were down sharply once again as Wall Street continued its volatile streak during the coronavirus crisis. The Dow Jones Industrial Average was down more than 1,300 points, or 6.3%. The S&P 500 and Nasdaq fell 6% and 5%, respectively. Those losses offset a sharp bounce from the previous session, which was sparked by hopes of massive fiscal stimulus. —Imbert

11:43 am: Aerospace and Defense stocks on pace for worst month ever

The iShares U.S. Aerospace & Defense ETF is down 41% in March, on pace for its worst month ever back to its inception in 2006. The index is led lower in part by Spirit Aerosystems, Boeing, TransDigm, all on pace for their worst months ever. Spirit Aerosystems is down almost 68% this month, on pace for its worst month ever back to its IPO in 2006

Boeing is down over 62% this month, on pace for its worst month ever through 1972

TransDigm is down almost 57% this month, on pace for its worst month ever back to its IPO in 2006 — Francolla, Fitzgerald

11:35 am: Amid the market volatility, analysts say buy these stocks: Zynga, Kroger, Hershey, Ralph Lauren & more

Morgan Stanley downgraded Coca-Cola and Monster Beverage to equal weight from overweight.

Bank of America upgraded Tesla to neutral from underperform.

Bank of America downgraded Levi Strauss to neutral from buy.

Bank of America upgraded Ralph Lauren to buy from neutral.

Credit Suisse upgraded Hershey to outperform from neutral.

Telsey upgraded Kroger to outperform from market perform.

Bernstein upgraded Campbell Soup, General Mills, Conagra Brands and Kellogg to market perform from underperform.

Oppenheimer initiated Zynga as outperform.

Oppenheimer initiated Sony as outperform.

Credit Suisse named Constellation Brands a top pick.

JPMorgan upgraded D.R. Horton to overweight from neutral and downgraded Lennar and PulteGroup to neutral from overweight.

Credit Suisse upgraded Walmart to outperform from neutral.

BTIG upgraded Dunkin' Brands to buy from neutral.

Goldman Sachs added O'Reilly Automotive to the conviction buy list.

Barclays downgraded American Airlines to equal weight from overweight.

Longbow upgraded Domino's to buy from neutral.

Nomura Instinet initiated Stitch Fix and The RealReal as buy.

UBS upgraded Caterpillar to neutral from sell. Read more on the analyst calls of the day here. — Bloom

11:32 am: Oil plummets 16% to more than 18-year low, on pace for worst month ever

Oil plummeted 16% to a more than 18-year low on Wednesday as the coronavirus pandemic continues to sap demand for crude and as rising worries about a global recession lead to fears of longer-term demand destruction. U.S. West Texas Intermediate crude fell 16.1%, or $4.35, to $22.60 per barrel. International benchmark Brent crude shed 9.4%, or $2.71, to trade at $26.02, its lowest level since 2003. Oil is getting hit on both the supply and demand side. A slowdown in worldwide travel and business activity is weighing on demand, just as powerhouse producers Saudi Arabia and Russia prepare to ramp up production. - Stevens

11:15 am: Dow tanks 1,400 points

The sell-off deepened in late-morning trading, with the Dow plummeting more than 1,400 points. The S&P was down 6%, threatening to trigger a key exchange-mandated circuit breaker. If the S&P 500 drops 7%, trading will pause for 15 minutes.— Li

10:40 am: Emerging Markets ETF on track for worst month since 2008

The iShares MSCI Emerging Markets ETF (EEM) is down 6%, bringing its month-to-date losses to more than 21%. The ETF is on track for its worst month since October 2008. — Francolla, Stevens

10:35 am: Walmart jumps 5%, gets an upgrade from Credit Suisse

While the broader market moves lower, shares of Walmart are up more than 5% as Credit Suisse upgraded the stock to an outperform rating on Wednesday. "We see this unfortunate period accelerating structural changes in consumer shopping, possibly by 5+ years, as they are introduced to new retailers and new shopping methods," the firm said. Credit Suisse raised its full-year 2021 earnings estimates, saying the multi-channel retailer will benefit from a jump in online grocery and delivery, among other things. – Stevens

10:24 am: Market comes back a tad, Dow now down 950 points

Stocks rebounded slightly from their steep opening losses. The Dow traded about 950 points lower after plunging 1,365 points at its low. The S&P 500 dropped 4% after tanking 5.6% at the open. Wall Street's fear gauge the Cboe Volatility Index, known as the VIX, fell 6% to about 71, after hitting a record close of 82.69 on Monday. -- L

9:48 am: Bernanke, Yellen push Fed to buy corporate bonds

Former Federal Reserve chairs Ben Bernanke and Janet Yellen are urging the central bank to buy corporate bonds. Though the authority to do goes beyond the central bank's authority, it can get the permission from Congress. Bernanke and Yellen said doing so would "help restart" the investment-grade part of the market that "is under significant duress." – Cox

9:46 am: Investor Ackman says Trump should shut down US, says markets would 'soar'

Investor Bill Ackman advised President Donald Trump on Wednesday to shut down the U.S. for one month in an effort to contain the novel coronavirus and said financial markets would rally in response to such decisive action. Ackman, who founded Pershing Square Capital Management, called on the president to both close the nation's borders as well as offer Americans a one-month rent, interest and tax holiday. "The moment you send everyone home for Spring Break and close the borders, the infection rate will plummet, the stock market will soar, and the clouds will lift," the hedge fund manager wrote. — Franck

9:40 am: Deutsche sees US GDP cratering 13%

The U.S. economy will contract by 13% in the second quarter because of the coronavirus pandemic, Deutsche Bank said in a new forecast. A drop that sharp would be "significantly beyond the range of modern historical experience," the firm said, and would be the biggest "going back to at least World War II." — Sheetz

9:39 am: Circuit breakers could be triggered again

Wild swings continued to roil Wall Street on Wednesday, with the S&P 500 dropping more than 5% at the open. The market is at risk to trip the so-called circuit breakers for the second time this week. According to the New York Stock Exchange, a market trading halt may occur at "three circuit breaker thresholds" on the S&P 500 due to large declines and volatility. The exchange classifies this at three levels based on the preceding session's close in the S&P 500.

The rules, which apply to regular trading hours only, are as follows:

· Level 1: If the S&P 500 drops 7%, trading will pause for 15 minutes.

· Level 2: If the S&P 500 declines 13%, trading will again pause for 15 minutes if the drop occurs on or before 3:25 p.m. ET.

· Level 3: If the S&P 500 falls 20%, trading would halt for the remainder of the day. A Level 3 breach can be triggered at any time. — Li

9:31 am: Dow tanks 1,300 points at the open

The Dow Jones Industrial Average plunged 1,300 points at the open, while the S&P 500 dropped more than 5%, at risk of triggering a market-wide circuit breaker for the second time in just three days. If the S&P 500 drops 7%, trading will pause for 15 minutes. — Li

9:13 am: Boeing stock on pace for worst month ever

Shares of Boeing tanked another 20% in premarket trading on Wednesday, bringing its losses this month to a whopping 64%. The plunge put the aircraft manufacturer on track for its worst month in history. On top of the consequences of two fatal crashes of its 737 Max aircraft, Boeing took a big hit from the coronavirus outbreak that disrupts the global supply chains and the travel industry. The second worst month for the company was in September 2001, when the stock lost nearly 35%. – Li, Francolla

8:51 am: Sterling tumbles to lowest level since 2016 against the dollar

Sterling slid below $1.19 on Wednesday to hit its lowest point since October 2016 as liquidity concerns sent the dollar surging and hammered currencies around the world. The pound fell 1.5% on the session to hit $1.1873, its lowest level since an overnight flash crash in October 2016 and below the levels seen in the aftermath of the Brexit referendum. —Smith

7:53 am: Oil prices continue to slide, hit lowest levels since 2003

The price of oil continues to fall as the coronavirus pandemic leads to major economies restricting movement within major cities and expectations of a recession grow. West Texas International futures have declined 5.8% to trade at $25.38 a barrel and hit its lowest level since 2003. Futures for International benchmark Brent crude slipped about 3.5% and are trading at under $28 per barrel. — Pound

7:51 am: Treasury yields charge higher after White House floats $1 trillion stimulus plan

Long-term U.S. debt yields continued to rise on Wednesday after Treasury Secretary Steven Mnuchin said the White House would like to see a $1 trillion stimulus package to help insulate the economy from a downturn. The prospect of such a massive stimulus plan and a deluge of additional U.S. debt put outsized pressure on Treasury prices and sent the 10-year yield up more than 30 basis points on Tuesday. The 10-year rate, often used by banks as a benchmark for loans, has ripped from around 0.65% on Monday to 1.11% at the latest reading. — Franck

7:38 am: Regeneron rises on hopes of coronavirus drug

Shares of biotechnology company Regeneron rose nearly 2% in premarket trading on Wednesday, the day after the company said it aims to have doses of a potential drug for COVID-19 ready to start human clinical trials by early summer. The antibody is believed to be a treatment for the virus, as well as a preventative drug. Shares of Regeneron rose more than 11% on Tuesday. – Fitzgerald

7:35 am: Coronavirus cases jump, worrying Wall Street

A spike in coronavirus cases continues to worry investors, who are hoping for government stimulus to offset the economic impacts of the virus. Worldwide coronavirus cases top 200,000 for the first time, according to data compiled by John Hopkins University. Italy has more than 2,500 virus related deaths as of Tuesday evening, the country's health ministry said. Iran's death toll from the coronavirus climbed to 1,135 with 147 new deaths in the past 24 hours, a health ministry official told state TV on Wednesday. The total number of infected people across the country has reached 17,361. Plus, European leaders agreed Tuesday to close the European Union's external borders for 30 days in a new effort to slow the spread of the coronavirus pandemic. Singapore, Hong Kong and Taiwan also reported a rise in cases. France, which has seen a sharp spike in cases in recent weeks, said it could start seeing a slowdown of coronavirus infections in about eight to 12 days following the government's decision to lock down the country, Health Minister Olivier Veran said Wednesday. —Fitzgerald

7:28 am: Gundlach says it's 'ludicrous' to think US won't enter a recession

DoubleLine Capital CEO Jeffrey Gundlach believes there's a 90% chance the United States will enter a recession this year. The "Bond King" said that last week his odds stood at 80%, but that as the coronavirus outbreak continues to halt travel and shutter businesses worldwide, he now places the odds at 90%. Still, Gundlach added that he was incrementally less negative on the market's outlook given the magnitude of the federal government's response. "I think you're supposed to be staying liquid, I think you're supposed to be waiting for opportunities," he said. "We all know that the stock market is down a lot. We know the junk bond market's down a lot. ... Will the market snap back? Of course it will." —Stevens

7:25 am: Dow futures indicate 1,000-point drop