What has made the cyclospora behind the US outbreak so challenging to trace?

The FDA continues investigating Taylor Farms as the likely source of a major cyclosporiasis outbreak. Despite withdrawing some early test results, data still supports the link to the company's lettuce. At least 1,644 people have fallen ill, though actual numbers may be higher. Consequently, Taylor Farms voluntarily recalled shredded iceberg lettuce sourced from central Mexico. Health officials face significant challenges tracing the parasite, while the investigation focuses on the nation's largest recent cyclospora outbreak.