A record number of cyclospora cases have been reported in more than 30 US states, but experts say not every illness is likely to have been caused by a single source.

“Early information has shown lettuce as a common product that regularly comes up during the investigation,” said the Michigan health department.

Michigan, which is where much of the outbreak is centered, has reported over 4,300 cases of cyclosporiasis, which can cause diarrhea and a low grade fever.