The number of people affected by an outbreak of disease caused by tainted McDonald’s salad has now grown to 395, according to the Centers for Disease Control and Prevention. Sixteen individuals have been hospitalized, with cases recorded in 15 states. The illness is caused by the Cyclospora parasite, commonly associated with contamination from feces.

The infection takes at least a week or two to take hold, according to the CDC, and it may be up to six weeks before patients experience symptoms. The most common symptom is watery diarrhea, although patients might also experience a loss of appetite, weight loss, cramping, nausea and fatigue.

According to the latest information from the CDC, romaine lettuce that tested positive was put into pre-made salad packages by Fresh Express in Streamwood, Illinois. Those packages were shipped to McDonald’s locations, although not to retail consumers. However, romaine lettuce from the same batch was also packaged in pre-made salads by Caito Food of Indianapolis, Indiana. Those pre-made packages were shipped to locations nationwide. The pre-made salads and wraps were produced July 15 to July 18, 2018, and have a “Best By,” “Enjoy by,” “Best if Sold By” or “Sell By” date ranging from July 18 through July 23, 2018, according to the CDC.