Wyoming's cases of the intestinal parasite notorious for causing weeks of relentless diarrhea have more than tripled to 19 since July, with three people hospitalized.
Three other cases have been linked to a massive national Cyclospora outbreak involving iceberg lettuce from Taylor Farms de Mexico, and a fourth case will likely be added to that group, the Wyoming Department of Health told Cowboy State Daily on Thursday.
The numbers are a sharp jump from early July, when Wyoming had recorded six cases of cyclosporiasis, or "explosive diarrhea", the illness caused by the microscopic Cyclospora parasite.
This year's 19 cases make 2026 the second-highest Cyclospora year Wyoming has seen by this point, Wyoming Department of Health spokeswoman Monique McBride said.
And while much of the national attention has centered on contaminated lettuce, Wyoming has a smaller mystery of its own.
Three people are believed to have picked up the parasite inside Wyoming.
Investigators say they don't know where.
The cases aren't connected to one another, McBride said, and none has been linked to another known outbreak.
Dehydration
Cyclospora can be miserable, but Cheyenne Regional emergency physician Dr. Matthew Loptien told Cowboy State Daily earlier this summer that one of the biggest concerns isn't necessarily the parasite itself. It's what happens when the diarrhea just won't stop.
“The biggest thing that we worry about is dehydration,” Loptien said.
The microscopic parasite infects the small intestine, producing frequent watery diarrhea that can linger for weeks. Patients can also experience cramping, nausea, fatigue, loss of appetite and weight loss, and symptoms sometimes disappear only to return.
That prolonged illness can send people looking for answers — and Cyclospora isn't always an obvious diagnosis.
Loptien said identifying it can require specialized stool testing, and he suspects some infections are never diagnosed at all.
For people sick enough to seek treatment, Loptien said doctors are particularly concerned about replacing the fluid and electrolytes lost through prolonged diarrhea. More severe dehydration can require IV fluids.
Once Cyclospora is identified, the infection can be treated with the antibiotic combination trimethoprim-sulfamethoxazole, commonly known as Bactrim.
The parasite is generally picked up through contaminated food or water rather than passed directly from one sick person to another.
And this summer, investigators eventually found one enormous source: iceberg lettuce.
The Lettuce Outbreak
State health officials previously said the three confirmed patients apparently ate at Taco Bell restaurants while traveling in other states.
Federal trace-back investigators ultimately converged on Taylor Farms de Mexico, a central Mexico-based processor that supplied iceberg lettuce eaten by people who later became sick.
On July 17, Taylor Farms de Mexico pulled all iceberg lettuce sourced from central Mexico from the U.S. market. The recall included some Marketside iceberg salad and shredded lettuce products sold at Walmart, along with lettuce supplied to restaurants and other food-service operations.
Taco Bell stopped using lettuce from Taylor Farms de Mexico the same day.
Taylor Farms also suspended iceberg lettuce sourcing and production from central Mexico and temporarily stopped all production at its central Mexico facility.
"We are deeply concerned for everyone who has fallen ill and their families," the company said in a public statement.
Taylor Farms has also pointed out an unusual wrinkle in the investigation: product testing had not produced a confirmed positive Cyclospora sample as of Aug. 20.
Federal health officials nevertheless say the epidemiological and trace-back evidence shows Taylor Farms de Mexico iceberg lettuce was contaminated with Cyclospora and made people sick.
Should You Toss Your Lettuce?
The latest best-by date on the recalled products was Aug. 3, McBride said.
"The affected products should no longer be on store shelves and, hopefully, no longer in anyone's kitchen," she said.
Wyoming is not among the federal government's list of states where the recalled food was distributed.
FDA listed 31 other states and said recalled products were sold at select Walmart stores in 15 states, also not including Wyoming.
The Wyoming Department of Health referred questions about whether any implicated lettuce actually entered Wyoming to the Wyoming Department of Agriculture, which handles trace-backs and recalls.
Earlier this week, state epidemiologist Matt Peterson said these cases are scattered around Wyoming and don't appear related. Testing determined they aren't connected to the national lettuce outbreak.
Another 10 Wyoming cases this year have been associated with travel to Mexico. Two others involved domestic travel.
Wyoming typically sees only three to five sporadic Cyclospora cases in a year, Peterson said.
A Record-Breaking Outbreak
What's happening in Wyoming is a tiny piece of an extraordinary Cyclospora year unfolding across the country, and the numbers are still climbing.
The CDC posted an update Thursday showing 11,458 illnesses in 20 states linked specifically to the Taylor Farms de Mexico iceberg lettuce outbreak.
At least 495 people have been hospitalized and two have died.
That's up from 10,930 illnesses and 454 hospitalizations one week ago.
On Aug. 13, the outbreak stood at 9,481 cases. On Aug. 5, it was 6,358.
Go back to July 24 and investigators had identified 1,947 cases.
In barely a month, the recognized size of the outbreak has grown nearly sixfold.
The outbreak is now the largest recorded Cyclospora outbreak in U.S. history.
Cyclospora cases have been climbing nationally for years, with notable increases beginning about a decade ago and particularly large spikes in 2018 and 2019.
Nothing, however, has approached the scale of 2026.
Kolby Fedore can be reached at kolby@cowboystatedaily.com.
