Cyclospora Outbreak Hits 34 States as CDC Searches for Food Source

Symptoms and Diagnosis

Cyclosporiasis primarily affects the digestive system, causing symptoms that include nausea, bloating, and excessive gas. The hallmark symptom is watery, sometimes explosive, diarrhea. Unlike many other common gastrointestinal illnesses, such as norovirus, cyclosporiasis is not typically associated with significant vomiting or fever. The illness can be identified through a simple stool test, specifically a gastrointestinal PCR panel. Once diagnosed, it can be treated with the antibiotic trimethoprim-sulfa, which may help shorten the course of the infection. Medical professionals urge those experiencing persistent diarrhea or other gastrointestinal symptoms to contact their primary care provider. The CDC notes that those sickened in the current outbreak range in age from 5 to 88 years old. As of Thursday, there have been 141 hospitalizations nationwide and no reported deaths.

The Complexity of Investigation

Investigating *Cyclospora* presents unique challenges compared to other foodborne pathogens like *Salmonella* or *E. coli*. According to experts, *Cyclospora* cannot be grown in laboratory cultures, making standard subtyping methods unavailable. The CDC is currently relying on partial genotyping to connect cases, as the parasite’s genome is complex. Furthermore, there is an estimated six-week gap between the onset of illness and the reporting of cases to federal authorities. Investigators attempt to identify the source by interviewing patients about their recent food consumption, but because symptoms can appear anywhere from two days to two weeks or more after infection, patients often struggle to recall their full dietary history. Health officials are currently investigating several clusters of cases that may be epidemiologically linked, including a multistate outbreak involving Michigan, Ohio, West Virginia, and Kentucky.

For more on this story, see Cyclosporiasis Outbreak Hits 1,600 U.S. Cases as Officials Probe Water Source.

Transmission and Prevention

The parasite is transmitted through the fecal-oral route, typically by consuming contaminated food or water. Officials emphasize that the illness does not spread from person to person through casual contact. Gwen Biggerstaff, deputy director of the CDC’s Division of Foodborne, Waterborne, and Environmental Diseases, stated that the source of the outbreak is what people eat or drink. Previous outbreaks have been linked to various types of fresh produce, including:

• Bagged or processed salad greens
• Basil, cilantro, and parsley
• Raspberries and blackberries
• Snow peas and sugar snap peas

While preventing infection can be difficult because produce can be hard to decontaminate, health officials recommend several safety measures:

• Thoroughly rinse all fresh produce under running water, even if it is labeled as prewashed.
• Choose whole, unprocessed produce when possible.
• Cook produce when appropriate, as heating food to 158 degrees Fahrenheit or higher kills *Cyclospora*.
• Practice standard food safety, including washing hands with soap and water before and after handling fresh produce.

Context of the Outbreak

While it is typical for *Cyclospora* infections to rise during the spring and summer, the CDC reported that multiple states experienced a larger jump in cases over a two-week period compared to the same timeframe last year. In that period, only 249 cases had been reported nationally. State-level reporting often recognizes these increases before the data is compiled at the national level. Experts note that while the CDC’s Foodborne Disease Active Surveillance Network (FoodNet) monitors disease trends, it is not designed to identify emerging foodborne outbreaks. The current investigation is being managed by the CDC’s parasitic disease branch. Health officials continue to urge doctors to test for the condition and explicitly request laboratory testing on stool samples to ensure accurate reporting.

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