Markets turned cautious again, erasing an early gain and ending lower Wednesday as investors try to handicap how much the new coronavirus variant will impact the economy.

       The latest roller-coaster ride brought the S&P 500 index up early and down by the closing bell. The afternoon reversal is the latest dizzying move in recent days as the omicron variant spreads.

       Wall Street was already headed lower in the afternoon when the White House announced that the first confirmed case with the omicron variant had been found in the U.S., in a person who recently returned from South Africa.

       On Wednesday:

       The S&P 500 fell 53.96 points, or 1.2%, to 4,513.04.

       The Dow Jones Industrial Average fell 461.68 points, or 1.3%, to 34,022.04.

       The Nasdaq fell 283.64 points, or 1.8%, to 15,254.05.

       The Russell 2000 index of smaller companies fell 51.49 points, or 2.3%, to 2,147.42.

       For the week:

       The S&P 500 is down 81.58 points, or 1.8%.

       The Dow is down 877.30 points, or 2.5%.

       The Nasdaq is down 237.61 points, or 1.5%.

       The Russell 2000 is down 98.51 points, or 4.4%.

       For the year:

       The S&P 500 is up 756.97 points, or 20.2%.

       The Dow is up 3,415.56 points, or 11.2%.

       The Nasdaq is up 2,365.77 points, or 18.4%.

       The Russell 2000 is up 172.57 points, or 8.7%.