WASHINGTON (TheBlaze/AP) — Federal health authorities say more than 285 people in seven states have now been sickened with an unidentified stomach bug.

The Food and Drug Administration is investigating the cyclospora infections, which are often found in tropical or subtropical countries and have been linked to imported fresh produce in the past. It causes diarrhea and other flu-like symptoms.

cyclospora cayetanensis

(Image: CDC)

What investigators are not sure of is the source of the infection — how it is being spread.

The Centers for Disease Control and Prevention says the infection has been reported in Iowa, Nebraska, Texas, Wisconsin, Georgia, Connecticut and New Jersey. Most of the illnesses occurred from mid-June to early July. The CDC says it isn’t clear whether the cases are all linked.

cyclosporiasis map

Map of the distribution of the illness so far. (Image: CDC)

The illness is spread when people ingest foods or water contaminated with the microscopic parasite Cyclospora cayetanensis. The agency said it isn’t clear whether the cases are all linked. The CDC reported that no common events, like a social gatherings, have been identified in the cases of the illness under investigation.

cyclosporiasis

Different stages of the microscopic parasite as viewed through a microscope. (Image: CDC)

Watch this report about the illness: