McDonald’s on Monday reported disappointing quarterly revenue, dragged down by weaker-than-expected sales at its U.S. restaurants following an E. coli outbreak just weeks into the quarter.

Visits to McDonald's plunged because of an E. coli outbreak last fall — and so did its profits. Fourth-quarter sales at McDonald's locations open for at least one year fell 1.4% in the United States, a reversal compared to the same time period a year prior when sales rose 4.3%.