Foodborne illness outbreaks are often associated with familiar names such as Salmonella, Escherichia coli and Listeria. Yet one of the largest foodborne outbreaks in the United States this year has been caused by a microscopic parasite that many people have never heard of: Cyclospora cayetanensis. As of mid-July 2026, the US Centers for Disease Control and Prevention (CDC) had confirmed more than 1,600 laboratory-confirmed cases across 34 states, with over 5,000 additional illnesses under investigation and more than 140 hospitalisations. Despite weeks of intensive investigation, officials have not definitively identified the food responsible. This uncertainty illustrates one of the greatest challenges in modern food safety: Tracing contamination through complex fresh produce supply chains.

Biology and life cycle of the parasite

Cyclospora cayetanensis is a single-celled protozoan parasite belonging to the phylum Apicomplexa, the same broad group of organisms that includes the parasites responsible for malaria. Unlike bacteria, Cyclospora cannot multiply in food. Instead, it survives as environmentally resistant oocysts that require time outside the human body to become infectious. Humans are considered the only significant reservoir, and infection occurs when mature oocysts are ingested in contaminated food or water. The parasite invades cells lining the small intestine, causing the illness known as cyclosporiasis.

Why it is different from bacteria and viruses

One of the most unusual features of Cyclospora is its life cycle. Freshly excreted oocysts are not immediately infectious. They must remain in the environment for approximately one to two weeks before sporulating and becoming capable of infecting another person. Consequently, direct person-to-person transmission is uncommon. Instead, contamination usually occurs when irrigation water, wash water, soil or fresh produce becomes contaminated with human fecal waste. This characteristic distinguishes Cyclospora from many bacterial pathogens and places greater emphasis on agricultural water quality, sanitation and hygiene before food ever reaches consumers.

History of Cyclospora cayetanensis

Although Cyclospora gained widespread attention during produce-associated outbreaks in the 1990s, the organism was observed much earlier. Researchers first described unusual structures in human stool samples in Papua New Guinea in 1979. Throughout the 1980s scientists debated whether the organism was an alga, a cyanobacterium or another parasite. It became known as the ‘cyanobacterium-like body’ until advances in microscopy and molecular biology confirmed that it represented a previously unrecognised protozoan parasite. In the early 1990s it was formally named Cyclospora cayetanensis after Universidad Peruana Cayetano Heredia in Peru, where important early investigations were conducted.

Since then Cyclospora has emerged as an important foodborne pathogen worldwide. Numerous outbreaks have been linked to fresh raspberries, basil, cilantro, lettuce, salad mixes, snow peas and green onions. Almost all implicated foods share two characteristics: They are grown outdoors where contaminated irrigation water may be used, and they are typically consumed raw, eliminating the cooking step that would otherwise destroy many pathogens.

One of the landmark outbreaks occurred in 1996–1997 when more than 1,400 illnesses in the United States and Canada were linked to fresh raspberries imported from Guatemala. Subsequent investigations prompted significant improvements in agricultural practices. Other notable outbreaks include basil imported from Peru in 2005, bagged salad mixes in 2013, cilantro from Mexico in 2015, romaine lettuce served in restaurant salads and wraps in 2018, Fresh Express salad products in 2020 and several cilantro-associated outbreaks investigated between 2022 and 2024. Each event reinforced the importance of preventive controls at the farm level rather than relying solely on consumer washing.

Why traceback investigations are so difficult

The current outbreak highlights why Cyclospora investigations are particularly difficult. First, symptoms usually appear between two and 14 days after exposure, with an average incubation period of approximately one week. By the time illness develops, most people struggle to remember exactly what they ate. Few consumers can recall the origin of lettuce in a salad consumed days earlier, particularly when dining at restaurants.

Second, fresh produce is highly perishable. Unlike canned or packaged foods, there are rarely leftovers available for laboratory testing. Packaging is often discarded immediately, removing lot numbers and traceability information. Third, produce supply chains are extraordinarily complex. A single prepared salad may contain lettuce from one farm, herbs from another region and vegetables sourced through multiple distributors. Bagged salad products may combine leaves harvested from numerous farms before packaging. These factors make epidemiological investigations far more complicated than recalls involving a single manufactured product.

Cyclospora presents additional scientific challenges because it cannot be cultured routinely in laboratories in the same way as Salmonella or Listeria. Detection depends largely on specialised molecular methods and targeted stool testing, which may not be requested unless clinicians specifically suspect Cyclospora. Consequently, cases are likely underdiagnosed, delaying recognition of outbreaks.

Symptoms, diagnosis, and prevention

Individuals infected with Cyclospora commonly experience profuse watery diarrhea, abdominal cramps, bloating, nausea, fatigue, loss of appetite, weight loss and, occasionally, low-grade fever. Without treatment, illness may persist for weeks or months, with symptoms improving before recurring. The recommended treatment is trimethoprim-sulfamethoxazole, while supportive care focuses on preventing dehydration.

For consumers, washing fresh produce remains an important food safety practice, but it is not a guarantee against Cyclospora. The parasite can adhere firmly to leafy vegetables and herbs, and routine washing may not remove all oocysts. Prevention therefore depends primarily on good agricultural practices, safe irrigation water, proper sanitation facilities for farm workers and robust environmental monitoring programmes.

Lessons for Jamaica

Although the current outbreak is centred in the United States, it carries important lessons for Jamaica. The country imports a substantial quantity of fresh produce while simultaneously promoting agricultural exports and food tourism. Hotels, restaurants and processors increasingly depend on international supply chains. A contamination event anywhere along those supply chains can have consequences far beyond the country of origin. Strengthening Good Agricultural Practices (GAP), Hazard Analysis and Critical Control Point (HACCP) systems, water quality management, traceability and supplier verification will therefore remain essential to protecting public health and maintaining confidence in Jamaica’s food industry.

Climate change may further complicate this picture. Increasing temperatures, more frequent droughts and changing rainfall patterns influence water availability and quality, potentially increasing reliance on alternative irrigation sources. Where wastewater management is inadequate, the opportunity for contamination may also increase. Building resilient food safety systems capable of addressing these evolving risks is therefore becoming just as important as responding to outbreaks after they occur.

Cyclospora reminds us that food safety often begins long before food reaches our kitchens. A salad may appear fresh, wholesome and nutritious, yet contamination may have occurred weeks earlier through something as ordinary as irrigation water. The ongoing US outbreak demonstrates that preventing foodborne illness requires collaboration across the entire food chain — from farmers and processors to distributors, regulators, food service operators and consumers. As food supply chains become increasingly interconnected, the most effective defence against invisible hazards such as Cyclospora will continue to be prevention rather than reaction.

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About the Author

Allison Richards is a food safety communicator, certified trainer and the founder of The Food Safety Girl, a consumer awareness platform promoting food safety in Jamaica and the Caribbean. She is the Caribbean Chapter Director for Women in Food Safety (WIFS) and host of The Big Bite Food Safety Show. With over 14 years of experience in food safety regulation, she is committed to public education and consumer empowerment. Through public education initiatives, including free community webinars, she continues to create space for learning, dialogue, and practical food safety awareness.

Allison Richards thefoodsafetygirlja@gmail.com.