The outbreak involves Fresh Express items used in the McDonald's salads that were contaminated with the parasite Cyclospora.
McDonald's has stopped selling those salads at some 3,000 restaurants, all located in Midwest states: Illinois, Iowa, Indiana, Wisconsin, Michigan, Ohio, Minnesota, Nebraska, North Dakota, South Dakota, Montana, West Virginia and Missouri.
People who purchased salads while traveling through the Midwest from other states include residents of Tennessee and Virginia as well as the Connecticut resident.
Of the hundreds sickened, 20 were hospitalized with severe symptoms.
McDonald's stopped selling salads at impacted restaurants on July 13. Fresh Express was not identified as the salad mix supplier until Aug. 1.
Most people infected with Cyclospora develop diarrhea, but other symptoms can occur, including weight loss, loss of appetite, bloating, increased gas, nausea, fatigue, vomiting, fever, and abdominal cramps.
If untreated, symptoms can persist for several weeks or a month or more.
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