US Faces Worst Cyclospora Outbreak: Health Officials Investigate

Infections from the parasite cyclospora are surging nationwide, with 2026 already marked as the worst year on record for reported cases. More than 30 states have reported infections, surpassing the previous US high of approximately 4,700 cases set in 2019. Federal health officials are investigating, noting that cases in at least four states—Michigan, Ohio, Kentucky, and West Virginia—may be linked.

Early investigations suggest lettuce as a common product associated with the infections. Michigan health officials have advised consumers to wash whole heads of lettuce thoroughly after discarding outer layers and to avoid bagged lettuce and salad kits. The FDA is conducting traceback investigations on various produce items.

The parasite infects the bowels and spreads through contaminated food or water. While the number of cyclospora cases has been rising for about a decade, experts attribute the increasing trend to climate change and improved detection methods. As of July 15, 2026, the CDC is aware of 1,645 confirmed domestic cases since May 1, with over 5,100 requiring further analysis, and case numbers are expected to grow through August.