Sewage-Irrigated Crops Emerge as Plausible Source of 22,000-Case U.S. Cyclospora Outbreak
Updated
Updated · The Washington Post · Aug 9
Sewage-Irrigated Crops Emerge as Plausible Source of 22,000-Case U.S. Cyclospora Outbreak
3 articles · Updated · The Washington Post · Aug 9
Summary
More than 22,000 U.S. cases and two Michigan deaths have pushed researchers to focus on sewage contamination of food as a leading explanation for the outbreak, though the government is still investigating.
Cyclospora spreads only through humans: infected people can shed 100 to 10,000 oocysts per gram of feces for up to 60 days, and those oocysts can survive sewage treatment, mature outdoors in about a week and return via irrigation water or produce.
Up to 25% of sewage samples in global studies have detected cyclospora oocysts, and the microbiologist estimates sewage could contain 1 to 100 oocysts per liter—levels that are hard to measure but still capable of causing disease.
About 200 billion gallons of treated U.S. wastewater are used each year to irrigate agricultural land, while few states specifically regulate removal or monitoring of protozoa such as cyclospora in treated sewage.
The theory adds to earlier traceback findings, including a 15-state outbreak linked to shredded iceberg lettuce from central Mexico, and suggests hotter weather, floods and drought-driven water reuse could raise future food and water risks.