How a Feces Parasite Landed in Our Food Supply

Human waste is at the center of the biggest cyclospora outbreak on record in the US, and investigators are trying to trace how it ended up on our plates. The parasite lives in people, passes out through diarrhea, and can later sicken someone who eats produce tainted with its eggs—often via contaminated irrigation water or the unwashed hands of farmworkers, per the New York Times. More than 6,000 people in Michigan alone have fallen ill, evidence of what one food safety microbiologist calls a "surprising scale" of fecal contamination in the food supply.

Cyclospora is tough to kill and challenging to wash off: Chlorine treatments target bacteria, not parasites, and the organism's "sticky" eggs cling to textured foods like raspberries and cilantro. Past outbreaks have been tied to Guatemalan raspberries that were contaminated with a pesticide-water mix fouled by latrine runoff, and to bagged salad traced to a Florida farm where a local irrigation canal tested positive for the parasite. Experts say a single sick worker is unlikely to explain the current surge; widespread contamination of water or equipment is more plausible.

After initial reports on the source were found to be erroneous, tracking down the precise source will require intensive environmental sampling, and time. The AP notes some of the roadblocks, including that some standard food-poisoning tests aren't designed to pick up on cyclospora. Reuters, which notes that lawsuits have already been filed connected to this outbreak reports that, in some past incidents, including a 2018 outbreak linked to salads from McDonald's that left more than 500 people sick, the source was never found.