The Dow Jones industrial average dropped 203 points, or 1.2 per cent, to 16,839 as of 12:54 p.m. Eastern time Wednesday.
The Standard & Poor's 500 index fell 18 points, or 0.9 per cent, to 1,953. The Nasdaq fell 57 points, or 1.3 per cent, to 4,435.
A closely watched index of U.S. manufacturing fell last month. Airlines stocks slid as investors feared that news of the first Ebola case in the U.S. might discourage travel. American Airlines and Delta each fell 3 per cent.
Still, the market remains close to all-time highs reached last month.
Government bond prices rose. The yield on the 10-year Treasury note fell to 2.41 per cent from 2.49 Tuesday.