Colorado has now recorded 178 cases of cyclosporiasis, the so-called “explosive diarrhea” parasitic illness, but state health officials still have not detected any indication of an outbreak here.
Out of those cases, public health workers have been able to complete investigations on 154 of them. Of those, only 18 of the infections are believed to have been contracted in the United States, said Hope Shuler, a spokesperson for the Colorado Department of Public Health and Environment.
The vast majority of the Colorado cases — more than 80% — have been linked to international travel, Shuler said.
The numbers are current as of Monday, when CDPHE updates weekly counts.
Cyclosporiasis continues to make headlines across the country, with Michigan alone reporting more than 7,000 cases as of Wednesday.
The Centers for Disease Control and Prevention has focused its outbreak investigation on five states: Michigan, Ohio, Indiana, West Virginia and Kentucky. But the investigation has been chaotic, with federal authorities first linking iceberg lettuce distributed by Taylor Farms to the outbreak and then later retracting the claim of a positive test result while saying that Taylor Farms lettuce is still the prime suspect. Adding to the chaos have been reports about possible political maneuvering by Taylor Farms, though whether politics played a role in the retraction is unproven.
Taylor Farms has conducted a voluntary recall of iceberg lettuce distributed to 27 states — a list that doesn’t include Colorado.
Amid all that, Colorado’s case counts are almost a relief, though of course the disease itself is brutal for those who catch it.
Colorado typically sees dozens of cyclosporiasis cases per year, mostly connected to international travel. Last year, Colorado recorded 204 cases for the entire year, putting the state on track to beat that number for 2026. Summer is typically the high season for cyclosporiasis.
It is unclear what may be driving the increased numbers this year, but one possibility is that the publicity around the outbreak nationally has led more people locally to be tested when they have an intestinal illness.
Shuler said five of the Colorado cases this year reported spending time in states that are part of the multistate outbreak. She said, among the handful of cases where those afflicted did not report traveling outside of Colorado, no common sources of infection have been identified.
Cyclosporiasis is caused by a parasite that typically hitches a ride on contaminated produce or water. It does not spread directly person-to-person.
Its most famous symptoms are the now-infamous trio of stomach cramps, gas and frequent, watery diarrhea. The disease is rarely fatal, but it can cause hospitalization due to dehydration.
In Colorado this year, four people have been hospitalized due to cyclosporiasis, according to CDPHE.