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In 2022, Florida's reported cases of cyclosporiasis — an intestinal infection caught from contaminated food or water — doubled, from 254 to 513. Part of the rise traced back to one product: a brand of Caesar salad kit sold by a single grocery chain. The investigation is a good example of how genetic testing and patient interviews, used together, can connect scattered cases.
The parasite
| Cause | Cyclospora cayetanensis, a single-celled parasite that infects only humans |
| How it spreads | swallowing its oocysts in food or water contaminated with feces |
| History | illness first reported in 1979; the organism identified and named in 1994 |
| Washing produce | reduces the parasite but does not eliminate it |
It used to be picked up mostly abroad, or from imported produce. Now it has been found on produce grown in the United States, and U.S. cases have climbed:
| Year | U.S. cases reported |
|---|---|
| 2016 | 537 |
| 2017 | 1,194 |
| 2018 | 3,519 |
| 2019 | 4,703 |
Florida, 2022
- 513 cases: 486 confirmed by laboratory, 27 probable — double 2021's 254, after a decade of rising numbers.
- 91% fell ill between May 1 and August 31, peaking in early July.
- 276 patients' specimens went to CDC's Cyclospora genotyping project; 211 were matched to a genetic cluster.
Florida cyclosporiasis cases by onset date, May–August 2022. CDC, MMWR
Finding the salad
Florida required county health staff to interview every patient who fell ill in that window, using CDC's national questionnaire for generating hypotheses about the source.
| Of the questionnaires | |
|---|---|
| Completed | 457 |
| Had not travelled abroad | 330 (72%) |
| Of those, ate bagged salad | 200 (61%) |
| Of those, named one brand of Caesar salad kit (romaine only) from one chain | 85 (43%) — ill between June 23 and July 16, median onset July 1 |
| Ate Caesar kits but could not name the brand, or bought them elsewhere | 76 more — 161 potentially linked in all |
The genetic check
CDC genotypes Cyclospora in near-real time to help link cases. Of Florida's 211 genotyped specimens, 153 (73%) belonged to the same genetic cluster — including 43 of 45 specimens from the salad-kit group, and 30 of the 76 people who could not name the brand.
The findings, and details of the product from the grocery chain, went to the Food and Drug Administration to trace it back to its source. The contaminated source was not identified.
What it shows
The genetic data and the interviews agreed strongly. Together — the questionnaire pointing at a food, genotyping confirming which cases belong together — they make a stronger case for a common source than either alone, and the approach can guide future outbreak investigations. Bagged salads have been linked to cyclosporiasis outbreaks before.
Sources
Written from "Notes from the Field: Doubling of Cyclosporiasis Cases Partially Attributable to a Salad Kit — Florida, 2021–2022," by Paul Rehme, Florida Department of Health, Morbidity and Mortality Weekly Report 72(27), CDC; a work of the United States government in the public domain. It cites Ortega and Sanchez (2010), Barratt and others (2022), Hoang and others (2005), and the FDA's first documented Cyclospora contamination of U.S. produce (2018).
Licenza: CC0 1.0 (pubblico dominio) · Tratto da www.cdc.gov
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