A tropical parasite that causes weeks of explosive diarrhea has sickened at least 145 people across 17 states and hospitalized 20, and the Centers for Disease Control and Prevention says it still can't find a common cause — and won't ask the obvious question about what's walking across the open southern border.

The CDC confirmed 145 cases of cyclosporiasis as of mid-June, with New York, Texas, and Illinois hit hardest, according to Fox News. But Michigan is now bearing the brunt: the Detroit Free Press reports more than 225 cases across 21 counties and the city of Detroit as of July 1, a number state officials call "large and growing." ClickOnDetroit put the Michigan count at 170 — with the discrepancy likely reflecting the rapid pace of new infections. Either way, Michigan normally sees only about 50 cases per year. The outbreak has crossed into Ohio as well, where the Toledo-Lucas County Health Department is investigating 65 additional cases.

The culprit is Cyclospora cayetanensis, a microscopic parasite the Detroit Free Press notes is "common in tropical and subtropical parts of the world." People get sick after eating food or drinking water contaminated with feces carrying the pathogen. The CDC says the parasite needs one to two weeks outside the body before it becomes infectious, making direct person-to-person spread unlikely.

So where is it coming from? The Detroit Free Press reported that "fresh produce imported to the U.S. from these regions can be contaminated with the pathogen" and that people can also get sick "after traveling to parts of the world where cyclospora cayatenensis is endemic." ClickOnDetroit noted that U.S. outbreaks have been "linked to various types of fresh produce."

What neither the CDC nor any of the three outlets will ask: with millions of crossings at a southern border that this administration has left wide open, what pathogens are hitching a ride? The same federal agency that tracked your church attendance during COVID and shut down your livelihood over a virus now can't — or won't — connect the dots between a tropical parasite endemic to the Global South and the unprecedented flow of migration from those same regions.

The CDC noted flatly that "there is currently no evidence of a single, multistate Cyclospora outbreak linking all cases," per Fox News. Maybe that's true. But there's also no evidence the agency has seriously investigated whether the border crisis is a vector. Absence of evidence, in this case, is evidence of absence — of curiosity.

Michigan health officials issued an alert June 30 urging doctors to test stool samples from patients with symptoms and report positives within 24 hours. Patients range from children to the elderly, with a median age around 42. Women make up 61% of cases. Symptoms include watery and sometimes "explosive" diarrhea, severe abdominal cramping, bloating, nausea, fatigue, and weight loss that can drag on for a month or more without antibiotics.

The public gets the usual advice: wash your produce, wash your hands. Sound guidance, as far as it goes. But the CDC is telling Americans to scrub their vegetables while refusing to scrub the border. The agency that locked you down now wants you to believe a tropical parasite spreading across two dozen states is just a produce-washing problem.

The question isn't whether every case came across the border. The question is why the agency tasked with disease surveillance refuses to even look.