My eldest son just spent a week at sleepaway summer camp. He had a great time. Sleeping under the stars, building campfires, hiking through the woods. When I picked him up this past weekend, he presented with the symptoms I’ve come to expect after his annual commune with nature: abundant bug bites, sunburn, exhaustion, and a lingering smell that I can only describe as “campy.” But an email from camp officials has my family on the lookout for a more concerning aftereffect—cyclosporiasis.
The camp said that there may have been a problem with the lettuce served in the dining hall. “At approximately 8:15 PM on Friday, July 17, [the camp] received notification from US Foods that certain lots of lettuce delivered to camp during session 7 were included in a voluntary recall due to the potential presence of Cyclospora cayetanensis, a parasite that can cause an intestinal illness known as cyclosporiasis,” the email read. “The recalled lot numbers included lettuce that had already been served to campers and staff prior to our receiving the notification.” Camp administrators discarded the affected lettuce, and they were not yet aware of any confirmed cases of cyclosporiasis, which can cause long bouts of watery diarrhea, loss of appetite (duh), and a suite of other unpleasant gastrointestinal symptoms, the email added.
Read more: “Parasites Are Us”
The thing is that Cyclospora, a spore-forming, microscopic protist that functions as an obligate intracellular parasite, takes its sweet time setting up shop in an infected person’s small intestine. Cyclospora’s incubation period is 2 to 14 days due to its habit of sporulation. When someone ingests a spherical cell of Cyclospora, the parasite deploys its oocysts to invade the lining of the host’s small intestine. There, the oocyst (literally “egg sac” in Latin), incubates for about a week, releasing cellular components called sporozoites that penetrate the host’s epithelial cells, where they reproduce asexually to create daughter cells. These daughter cells can either infect neighboring host cells and undergo another round of asexual reproduction or reproduce sexually to create zygotes that mature into oocysts, rupturing the cell, passing the contents into the excrement of the infected person. The length of this process is both why cyclosporiasis is so hard to tie to a specific source (who, after all, can recall exactly what and where they ate 10 or 14 days ago?) and why the oocysts are not immediately infectious, making person-to-person transmission unlikely.
Detecting Cyclospora in food sources is a vexing aspect of tracing the parasite’s march through a population’s guts. Because it cannot be readily cultured in labs, as can E.coli and Salmonella, for example, Cyclospora evades traditional detection methods, such as polymerase chain reaction to amplify sections of characteristic DNA.
Another reason this particular outbreak of cyclosporiasis has proved frustrating to such a wide swath of unfortunate victims—in Michigan, Indiana, Kentucky, Ohio, and West Virginia—and public health officials is because the U.S. Centers for Disease Control and Prevention, under the administration of President Donald Trump, cut its Foodborne Diseases Active Surveillance Network (FoodNet) program in 2025. That year, the FoodNet program surveillance was scaled back to just Salmonella and Shiga toxin-producing E. coli (STEC), foodborne pathogens that cause periodic outbreaks of illness in the U.S. and elsewhere. No official analysis has yet tied the FoodNet cuts to the breadth of the current outbreak, which is much larger than typical years. But the pathogenic organisms cut from FoodNet last year? Campylobacter, Listeria, Shigella, Vibrio, Yersinia, and you guessed it … Cyclospora.
On Saturday, the day I picked my son up from camp, the CDC officially linked the outbreak to contaminated iceberg lettuce imported from central Mexico. This was the recalled lettuce my son may have eaten at camp. With thousands of people suffering from confirmed cyclosporiasis and thousands more awaiting confirmation of infection from CDC analysis, the picture of this outbreak is still coming into focus on a regional and national level. Much will be discussed and written about what went wrong, what government health agencies can do to better avoid and react to such outbreaks, and how this intelligence should help us combat the next rash of food-borne illnesses.
But at our house, thanks to Cyclospora’s particular incubation cycle, we’re on diarrhea watch for the next couple of weeks. 
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Lead image: stockphoto mania / Adobe Stock
