--- title: "A Parasite Behind an 'Explosive' Stomach Illness Is Spreading. Here's What to Know" description: "Federal health officials are tracking a rise in cyclosporiasis, an intestinal illness caused by a parasite that spreads through contaminated food and water and produces bouts of watery, sometimes 'explosive' diarrhea. Here is what the CDC says about the symptoms, the risk and how to avoid it." category: "U.S." category_url: https://herald.la/category/us author: "Anjali Rao" published: 2026-07-02T08:50:40.000Z updated: 2026-07-02T08:50:40.000Z canonical: https://herald.la/article/a-parasite-behind-an-explosive-stomach-illness-is-spreading-here-s-what-to-know tags: ["health", "CDC", "cyclosporiasis", "food safety", "outbreak"] --- # A Parasite Behind an 'Explosive' Stomach Illness Is Spreading. Here's What to Know Federal health officials are tracking a rise in cyclosporiasis, an intestinal illness caused by a parasite that spreads through contaminated food and water and produces bouts of watery, sometimes 'explosive' diarrhea. Here is what the CDC says about the symptoms, the risk and how to avoid it. Every summer brings a familiar unwelcome visitor to the United States: cyclosporiasis, a parasitic infection that arrives with the season's fresh produce and, this year, appears to be climbing again. Here is a plain-language guide to what it is and how to stay clear of it. ## The illness, and the numbers Cyclosporiasis is caused by *Cyclospora cayetanensis*, a microscopic parasite spread when food or water contaminated by feces is consumed. The U.S. Centers for Disease Control and Prevention, which tracks cases each year, [had logged well over 100 domestically acquired cases across more than a dozen states by mid-June](https://www.cdc.gov/cyclosporiasis/php/surveillance/index.html), a tally that typically climbs through the summer. State health departments have reported local surges: Michigan health officials, for instance, [warned of an unusual cluster of cases](https://www.michigan.gov/mdhhs/inside-mdhhs/newsroom/2026/07/01/cyclosporiasis) well above what the state normally sees. Investigators had not yet pinned the current cases to a single food source. ## Symptoms to watch for Symptoms usually appear about a week after infection. The hallmark is frequent, watery diarrhea — which some patients describe as "explosive" — often accompanied by stomach cramps, nausea, loss of appetite, fatigue and sometimes a low fever, [the CDC says](https://www.cdc.gov/cyclosporiasis/prevention/index.html). Left untreated, the illness can come and go over weeks. Most otherwise healthy people recover on their own, but people with weakened immune systems can have more severe or prolonged infections. ## How it spreads — and why hand-washing alone isn't enough Unlike some stomach bugs, cyclospora is not passed directly from person to person. The parasite needs one to two weeks in the environment after leaving the body before it can infect someone else, which is why outbreaks are tied to contaminated food and water rather than close contact. In the United States, past outbreaks have repeatedly been traced to fresh produce such as leafy greens, cilantro, basil and bagged salads. ## How to protect yourself The CDC's guidance is straightforward: rinse fruits and vegetables thoroughly under running water before eating or cooking them, wash your hands before preparing food, and, when traveling in areas where the parasite is common, stick to bottled or boiled water and avoid raw produce. Anyone with persistent watery diarrhea should see a doctor; cyclosporiasis is diagnosed with a stool test and treated with a common antibiotic, typically trimethoprim-sulfamethoxazole. Those who are sick should not prepare food for others until they have recovered. The CDC posts case updates on its cyclosporiasis surveillance page as its investigation continues. ## Sources - [Surveillance of cyclosporiasis](https://www.cdc.gov/cyclosporiasis/php/surveillance/index.html) - [Preventing cyclosporiasis](https://www.cdc.gov/cyclosporiasis/prevention/index.html) - [Outbreak of cyclosporiasis occurring in Michigan](https://www.michigan.gov/mdhhs/inside-mdhhs/newsroom/2026/07/01/cyclosporiasis)