The Centers for Disease Control and Prevention reported over 20,000 suspected cyclosporiasis cases this week, making this the largest outbreak of the diarrhea-causing parasite in U.S. history.

So far, the CDC has received reports of 10,468 confirmed cases of domestically acquired cyclosporiasis in 47 states. Another 12,255 cases have not yet been confirmed or investigated. If the latter group of cases is confirmed, the U.S. tally of cyclosporiasis cases would total more than 22,700.