People in at least another four states have been sickened by tainted McDonald’s salads.

Health officials in Wisconsin, Nebraska, South Dakota and Minnesota all report they now have cases of people infected by the Cyclospora parasite that they believe came from having eaten lettuce in salads at McDonald's. But the numbers, so far, are limited. Each of the states has two cases, except for Minnesota, which has three .

The new states join Iowa and McDonald's home state of Illinois -- the chain is based in Chicago -- who reported their outbreaks Thursday. So far, there are 16 cases in Iowa and 29 in Illinois.

The multi-state total is 54.

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Cyclosporiasis is a non-fatal infection and the most common symptom is watery diarrhea, according to the Centers for Disease Control. People fall ill an average of seven days after eating the food contaminated with fecal matter.

McDonald's said that until it can switch to another lettuce-blend supplier, the company was voluntarily halting sales of salads "out of an abundance of caution" at distribution centers and an estimated 3,000 restaurants. They're primarily in the Midwest -- the six impacted states along with Indiana, Kentucky, Michigan, Montana, North Dakota, Ohio and West Virginia.