Health authorities are cautioning Americans that a widespread “stomach bug” reported across the country may not be viral at all but rather a foodborne parasitic infection called cyclosporiasis.

The Centers for Disease Control and Prevention (CDC) has confirmed more than 1,600 domestic cases of cyclosporiasis since May, with another 5,100 currently under investigation across 34 states.

According to the CDC, the illness is caused by Cyclospora cayetanensis, a microscopic parasite that spreads through contaminated food or water.

CDC Deputy Director Gwen Biggerstaff said the agency is working to pinpoint the outbreak’s source and noted that individuals experiencing persistent diarrhea or abdominal cramps should consult a doctor about appropriate antibiotic treatment.

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In the Midwest, states such as Michigan and Ohio have seen a surge in reported infections, with many patients experiencing prolonged gastrointestinal distress.

Symptoms typically begin about one week after exposure but can appear anywhere between two days and two weeks after ingesting contaminated food or water.

Early signs often resemble those of a routine stomach virus, including nausea, abdominal pain and watery diarrhea, though some people may also experience fatigue, loss of appetite and weight loss.

Dr. Kenneth Perry, an emergency physician in South Carolina, explained that while routine stomach bugs usually resolve within 24 to 48 hours, Cyclospora infections last much longer and are marked by severe, foul-smelling diarrhea and abdominal cramping.

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Testing for the parasite can be done, but it requires a specific laboratory request since Cyclospora is not typically included in standard stool panels.

Diagnosis is made by examining stool samples, and repeated testing may be necessary because even symptomatic patients may not always shed detectable amounts of the parasite.

Perry emphasized that patients with lingering symptoms should visit their primary care physician rather than the emergency room, unless dehydration or other complications occur, since standard hospital tests often do not screen for Cyclospora.

He added that people who suspect exposure can check current FDA and CDC food safety alerts for advisories on recalled or contaminated items.

The infection is treatable with prescription antibiotics. The CDC recommends trimethoprim-sulfamethoxazole (TMP-SMX) as the standard therapy, while those allergic to sulfa drugs should consult their healthcare provider about alternatives.

Perry also advised patients to focus on hydration, using pediatric electrolyte formulas rather than typical sports drinks for optimal salt-to-sugar balance.

Anyone experiencing diarrhea lasting more than two to three days or showing signs of dehydration should contact a physician promptly.

CDC officials said they expect to identify the outbreak’s source soon as investigations continue across the affected regions.