US health officials investigate cyclospora outbreak across nine states

Federal health officials were investigating a cyclospora outbreak that had spread to nine states, while the Food and Drug Administration said the source had not yet been identified. The parasite causes cyclosporiasis, a diarrheal illness that can bring watery diarrhea, stomach cramps, fatigue, nausea and weight loss, and it often takes time to pin down because it can look like other stomach bugs.

The case map widened quickly. Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania and West Virginia were tied to the outbreak, and federal counts later reached nearly 2,000 confirmed cases. LiveNOW from FOX had put the illness count at 72 on July 23, showing how fast a multistate cluster can grow before investigators lock onto a source.

The FDA had begun traceback work, the supply-chain process investigators use to follow food back through growers, distributors and other handlers. One investigative thread pointed to shredded iceberg lettuce, a clue that fit cyclospora’s usual pattern of spread through contaminated fresh produce or unsafe water. The CDC also maintained an outbreak investigation page and a separate locations page for where sick people lived, a sign that public-health workers were still mapping the full footprint of the cluster.

The outbreak landed in a year when cyclospora surveillance was already under pressure. NPR reported on July 12 that a surge of cyclosporiasis cases had been detected in 34 states, and CDC changed cyclospora reporting to optional in 2025, a shift that can make it harder to track a parasite that crosses county and state lines. Public-health agencies have long depended on rapid case reporting to identify a contaminated ingredient before it reaches more kitchens, restaurants and grocery stores.

Cyclospora outbreaks are often linked to fresh produce because the parasite can travel through water used in growing or washing food, and severe illness can hit older adults and people with weakened immune systems especially hard. People with persistent watery diarrhea, stomach cramps, fatigue, nausea or weight loss after eating fresh produce or drinking potentially unsafe water need medical attention, because the illness can linger long enough to require testing and treatment before it clears.