The U.S. Food and Drug Administration (FDA) believes a multistate outbreak of cyclosporiasis illnesses that has affected more than 500 people is now over.

As of Sept. 11, a total of 511 people have been sickened from the infectious disease, which has been linked to a Fresh Express salad mix served at McDonald's restaurants.

The cases were reported by 15 states and New York City.

The FDA says it investigated distribution and supplier information for romaine and carrots but did not identify a single source or potential point of contamination for this outbreak.

McDonald's decided to voluntarily stop selling salads at impacted restaurants in numerous states on as of July 13. 

The company has since reported that it has replaced the supplier of salads in those states. More information can be found in McDonald's Statement.

On July 26, the FDA completed final analysis of an unused package of Fresh Express salad mix containing romaine lettuce and carrots, which had been distributed to McDonald's.

The analysis confirmed the presence of cyclospora in that sample, though the expiration date for that product, July 19, had already passed. On July 27, the FDA informed Fresh Express of the results.

On July 30, the USDA's Food Safety and Inspection Service (FSIS) issued a public health alert on beef, pork and poultry salad and wrap products potentially contaminated with cyclospora that were distributed by Caito Foods LLC, of Indianapolis, IN.