At least 269 people in eight states have been infected with a stomach illness since late June that has so far landed 10 people in the hospital.
The Center for Disease Control has yet to identify the source of cyclospora, a single-celled parasite that causes cyclosporiasis, an intestinal infection that causes diarrhea, stomach cramps, nausea and fatigue.
Cases have been confirmed in Iowa (127), Texas (65), Nebraska (68), Wisconsin (4), Georgia (2) and one each in Kansas, Illinois and Connecticut.
While cyclosporiasis is typically contracted by people living or traveling in the subtropics, or through produce imported from that part of the world, none of the infected have travelled internationally.
The CDC said it is cooperating with the U.S. Food and Drug Administration to pinpoint the source of the outbreak, which is spread when people ingest food or water contaminated with feces. It was also unclear if the cases are all from the same outbreak.