Cyclospora: Michigan alone reports 7,171 cases as FDA

Michigan has recorded 7,171 cases of cyclosporiasis, its health department reported on Wednesday — more than four times the 1,644 cases in the multistate outbreak that federal investigators have linked to shredded iceberg lettuce served at Taco Bell restaurants. The state figure covers all cyclosporiasis reported during the investigation period rather than only cases tied to the restaurant chain.

Why it matters

Two federal agencies and one state health department are describing what may be the same event in terms that do not fit together. The CDC counts 1,644 people across five states who ate at Taco Bell and fell ill, and the FDA has traced the shredded lettuce those restaurants used to a single Mexican supplier. Michigan, which accounts for a large share of the illness, counts 7,171 infections statewide and says on its own outbreak page that no produce type, grower or supplier has been identified. Both statements can be true at once — a multistate outbreak investigation only counts people who meet a case definition, while Michigan is counting every cyclosporiasis report it receives — but the gap between 1,644 and 7,171 is what the public actually sees, and neither agency is explaining it. Losing the only positive laboratory result in the middle of that makes the explaining harder, not easier.

The federal side of the investigation lost its only piece of laboratory evidence over the weekend. On Saturday the Food and Drug Administration said a sample of shredded iceberg lettuce supplied by Taylor Farms had tested positive for cyclospora. On Sunday it withdrew the finding. “Due to the complexity in detection of Cyclospora, FDA laboratory experts re-reviewed the sample results and have concluded that the finding does not represent true amplification and should be considered a false positive,” the agency said. As of Sunday there were no confirmed positive sample results at all.

The FDA said the reversal does not undermine its investigation, and the recall of iceberg lettuce grown in central Mexico remains in place. That position is defensible on its own terms: foodborne outbreaks are frequently solved by epidemiology and traceback rather than by recovering the pathogen from a sample, because suspect product is usually eaten or thrown away long before investigators reach it. But it does mean the case now rests entirely on where sick people ate and where that food came from.

Michigan’s own account differs from the federal one in a way the agencies have not publicly reconciled. The state’s outbreak page says that available information indicates lettuce or salad greens “may be a potential source,” while stating that “no specific type of produce, grower, or supplier has been identified as the source” and that other foods cannot be ruled out. The FDA, by contrast, names Taylor Farms de Mexico. Michigan has not adopted that conclusion for its statewide count.

The state data also show the scale. Michigan has reported cases in 65 of its 82 counties, and 102 people had been hospitalised as of July 16. The heaviest county totals as of that date were in the south-east — Wayne at 582, Washtenaw 474, Oakland 396 and Ingham 393 — with Monroe at 286 and Shiawassee, a far smaller county, at 278.

The age pattern in the Michigan figures is unusual for a foodborne outbreak, and it points back at the food. Of roughly 4,300 cases the state had classified by age as of July 16, just 20 were in children under ten — well under one percent. The cases cluster instead in the working-age bands, with people in their thirties the single largest group and the twenties and forties close behind. Cyclospora outbreaks are typically traced to fresh produce eaten raw, and salad greens are about the clearest example of a food that adults eat routinely and small children largely do not.

Counts of this illness are also unreliable in one direction. Cyclosporiasis is identified by a stool test that is not part of a routine workup, so infections are recorded only when a clinician thinks to order it, and mild cases that clear on their own are rarely captured at all. Both the federal and the state figures are therefore floors rather than estimates of how many people have been infected.

Illness onset dates in the federal outbreak run from May 13 to July 13. Michigan updates its statewide total each weekday morning, and its county, age and hospitalisation breakdowns on Thursdays.

Cyclospora: Michigan alone reports 7,171 cases as FDA retracts its only positive test

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