Investors are likely to see more big swings until the number of infections from the new coronavirus decelerate, market watchers say, and they also want a big, coordinated response from governments and central banks.

Stocks shook off an early loss and managed modest gains on Wall Street as traders remain cautious about rising tensions between the U.S. and Iran.

The S&P 500 soared 28.9% in 2019, and technology stocks push the Nasdaq up 35.3%.