Stocks on Wednesday closed with major gains after a string of major Democratic primary victories for former Vice President Joe Biden Joe BidenThe Memo: Warning signs flash for Trump on debates Senate Republicans signal openness to working with Biden National postal mail handlers union endorses Biden MORE and a flood of global central bank stimulus.

The Dow Jones Industrial Average closed with a gain of 1,173 points, a roughly 4.5-percent rise, as the S&P 500 rose 4.2 percent and the Nasdaq Composite rose 3.8 percent.

Wall Street analysts attributed Wednesday’s strong open to a rally in health care stock prices likely driven by Biden’s resounding Super Tuesday wins. Biden is seen among investors as less of a threat to the health care industry than his chief rival, Sen. Bernie Sanders Bernie SandersSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Schumer, Sanders call for Senate panel to address election security MORE (I-Vt.), who has proposed a nationalized health care system that would supplant private insurers.

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“I think this really has been well received on Wall Street as a wonderful Wednesday for Joe Biden,” said Jeff Kilburg, chief executive of investment firm KKM Financial, on CNBC.

Shares of health insurers Centene and Anthem skyrocketed more than 15 percent each, Humana shares rose more than 14 percent, and UnitedHealth Group and Cigna each rose more than 10 percent.

“A lot of participants view [Biden’s] strong showing as a healthier thing for the market if a Democrat ends up winning the White House because he’s a little more pro-business, so that’s helping,” wrote JJ Kinahan, chief market strategist at TD Ameritrade, in a Wednesday research note.

Market experts also credited the Federal Reserve’s emergency rate cut, subsequent cuts issued by central banks in Canada and China, and strong U.S. economic data released earlier Wednesday for the broader stock rally.

Private sector U.S. employers added 183,000 workers in February, according to the ADP National Employment Report released Wednesday.

Moody’s Analytics chief economist Mark Zandi, who compiles the report with ADP, said the survey was conducted before the first cases of coronavirus cases transmitted through community spread were confirmed in the U.S, but showed resilience in the labor market.

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Kinahan additionally cited Apple’s announcement Tuesday that it had begun reopening Chinese factories that were shuttered due to the coronavirus.

“It’s a combination of [Apple], Super Tuesday results, and perhaps some thoughts that we just overshot the mark yesterday in terms of negativity. People might be asking themselves, ‘Are things really that bad?’” Kinahan wrote.

Wednesday’s rally is the latest whipsaw in a stock market wracked by volatility as economists and investors brace for the coronavirus.

The Dow plunged 786 points Tuesday, taking a 2.9 percent loss, while the S&P and Nasdaq composite sunk 2.8 percent and 3 percent, respectively, even after the Fed’s emergency rate cut.

Updated 4:56 p.m.