The outbreak started in May and was caused by a parasite infection called Cyclosporiasis.
The Centers for Disease Control and Prevention said it has now sickened 507 people in 16 states; however, North Carolina is not one of them.
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Symptoms include diarrhea, vomiting, fever and body aches.
So far, 24 people have been hospitalized.
According to the FDA, an unused package of "Fresh Express" salad mix tested positive for the parasite.
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McDonald's said in July it had since removed the mix from impacted restaurants.
The states impacted are Connecticut, Florida, Iowa, Illinois, Indiana, Kentucky, Michigan, Minnesota, Missouri, Nebraska, Ohio, South Dakota, Tennessee, Virginia, Wisconsin and New York.