U.S. stocks spun lower in a dizzying day of trading Thursday as worries about the viral outbreak that started in China knocked the S&P 500 off its record high.

The market started the day higher following another round of stronger-than-expected reports on the U.S. economy, but it slumped suddenly in the late morning only to pare its losses later.

Market watchers didn’t see one clear trigger for the movements, which were reminiscent of the market’s sudden shifts during the height of the U.S.-China trade war. Several companies warned of the hit to profits they’re expecting due to the virus.

On Thursday:

The S&P 500 index fell 12.92 points, or 0.4%, to 3,373.23.

The Dow Jones Industrial Average fell 128.05 points, or 0.4%, to 29,219.98.

The Nasdaq lost 66.21, or 0.7%, to 9,750.96.

The Russell 2000 index of smaller company stocks rose 3.50 points, or 0.2%, to 1,696.07.

For the week:

The S&P 500 is down 6.93 points, or 0.2%.

The Dow is down 178.10 points, or 0.6%.

The Nasdaq is up 19.79 points, or 0.2%.

The Russell 2000 is up 8.49 points, or 0.5%.

For the year:

The S&P 500 is up 142.45 points, or 4.4%.

The Dow is up 681.54 points, or 2.4%.

The Nasdaq is up 778.36 points, or 8.7%.

The Russell 2000 is up 27.60 points, or 1.7%.