Fears over the coronavirus pandemic are prompting the New York Stock Exchange to prepare to implement an unprecedented contingency plan to close its iconic trading floor and switch to backup electronic trading systems.

The plan has some on Wall Street worried that it could lead to trading disruptions when markets are already fragile. The Dow Jones Industrial Average dropped 5.9%, sinking into a bear market Wednesday, the latest salvo in a barrage of volatility that has roiled the markets since February.