CDC Surveillance Data Show 145 Cyclosporiasis Cases in 17 States May-June 2023, Michigan Cluster Hits 300 With No Identified Vehicle

The CDC's notifiable disease system captured age-stratified incidence (median 42 years, 61 percent female) without travel history. Cases presented with watery diarrhea after a median 7-day incubation; 20 hospitalizations occurred and zero deaths. No single produce item or water source has been implicated despite trace-back by FDA and state agriculture departments. Michigan's Department of Health and Human Services is conducting case-control interviews focused on fresh produce consumed in late May and early June.

Past U.S. cyclosporiasis outbreaks have repeatedly traced to imported cilantro, basil, and raspberries, yet this season's multi-state pattern has not matched any single lot. The parasite requires 1-2 weeks of environmental sporulation, rendering person-to-person spread negligible and implicating upstream contamination during production or irrigation. Routine washing reduces but does not eliminate risk because Cyclospora oocysts adhere to produce surfaces and resist standard chlorine rinses.

Surveillance data remain incomplete; underreporting is likely because mild cases do not seek care and commercial labs vary in testing. The next required step is a published case-control study or whole-genome sequencing cluster analysis to identify the precise food vehicle before peak summer produce season ends.