The US has been hit by its worst ever Cyclospora outbreak, possibly caused by a parasite spread by lettuce.

The US has been hit by its worst ever Cyclospora outbreak, possibly caused by a parasite spread by lettuce.

Cases have been reported across more than 40 states including Michigan, New York and Ohio

Some US states are facing a large and growing outbreak of diarrhea caused by cyclospora, a microscopic parasite that can contaminate fresh food or water.

US officials claim evidence points to lettuce grown in Mexico, which Mexico's Health Ministry disputes.