Healthcare stocks have boosted Wall Street after a near sweep for Joe Biden in the Super Tuesday Democratic primaries, a day after markets suffered heavy losses following an emergency interest rate cut by the Federal Reserve.

The benchmark S&P 500 rose for the second time in 10 sessions, bolstered by Biden’s return to front-runner status in the US Democratic presidential nomination campaign over self-declared socialist Bernie Sanders.

“The markets will see Biden’s success as helping to eliminate what they see as the worst option, a Sanders presidency,” said Chris Nixon Cox, Chief Global Strategist at BrightSphere Investment Group.

Shares of health insurers UnitedHealth Group Inc, Centene Corp, Humana Inc and Cigna Corp surged between 9.8 per cent and 13.4 per cent.

The broader healthcare index jumped 3.2 per cent, the most among all the major S&P sectors trading higher.

The healthcare sector had suffered in recent months as Sanders and his “Medicare for All” proposal, which would eliminate private health insurance altogether, gained prominence.

The three indexes dropped nearly 3.0 per cent on Tuesday as an emergency interest rate cut by the Federal Reserve amplified fears about the extent of the economic damage from the coronavirus outbreak.

Fears of a global slide into recession, and a resulting collapse in US corporate earnings this year, have knocked $US3.1 trillion ($A4.7 trillion) off the value of major US companies in the past 10 days.

In early trading, the Dow Jones Industrial Average was up 445.37 points, or 1.72 per cent, at 26,362.78, the S&P 500 was up 37.97 points, or 1.26 per cent, at 3,041.34.

The Nasdaq Composite was up 88.84 points, or 1.02 per cent, at 8,772.93.

Adding to the upbeat mood, the ADP National Employment Report showed US private payrolls rose more than expected in February.

The data is considered a precursor to the more comprehensive jobs report on Friday.

All eyes will also be on the Fed’s beige book report, which will offer the first snapshot from the central bank’s business contacts on how deeply the coronavirus is impacting the domestic economy.

US food company Campbell Soup Co rose 5.9 per cent after lifting its 2020 profit forecast, and topping analyst estimates for the quarter on improved demand for its soups.

Upscale retailer Nordstrom slid 4.5 per cent after forecasting a 2020 profit largely below market expectations.

Advancing issues outnumbered decliners by a 4.39-to-1 ratio on the NYSE and a 2.88-to-1 ratio on the Nasdaq.

The S&P 500 recorded two new 52-week highs and 13 new lows, while the Nasdaq recorded 14 new highs and 35 new lows.