McDonald's salad has now sickened 507 people in 15 states, NYC

Last Updated Aug 24, 2018 10:16 AM EDT

An outbreak of intestinal illness linked to eating salads from McDonald's is widening.

More than a month after health officials first alerted the public, the count of confirmed cases tied to the cyclospora parasite has increased to 507 people, 24 of them hospitalized, and now includes residents from 15 states, the Food and Drug Administration said.

"The investigation is ongoing and the FDA is currently reviewing distribution and supplier information for romaine and carrots," the agency said in an update Thursday. A salad mix recalled by Fresh Express and distributed by Caito Foods is believed to have been the source for the parasite, the FDA said.

Health officials are investigating cyclospora illnesses associated with McDonald's locations in 11 states including Illinois, Iowa, Indiana, Kentucky, Michigan, Minnesota, Missouri, Nebraska, Ohio, South Dakota and Wisconsin. A Florida resident also became ill after purchasing a salad while traveling in Kentucky, while patients residing in Tennessee, Connecticut, Virginia and New York City purchased salads while in Illinois.

Transmitted in foods tainted by fecal matter, cyclospora can cause stomach cramps, nausea and flu-like symptoms a week or more after someone consumes food or liquid contaminated with the parasite.

The outbreak, first reported in Illinois and Iowa, prompted the fast-food chain to temporarily stop selling salads at the restaurants identified as possible sites of contamination. The company also said it was switching lettuce suppliers.