There is probably never going to be good news when it comes to an intestinal parasite capable of causing weeks of explosive diarrhea. But there is this: Despite recent, often dramatic, national reports about the spread of the parasite known as cyclospora, Colorado is not seeing an unusual number of cases.
There aren’t any outbreaks in Colorado of the disease, which is called cyclosporiasis. It’s not even the second-most common intestinal parasitic disease we have. It doesn’t spread person-to-person. And it sickens only about half as many people annually as the giardia parasite, which is the state’s actual chart-topper for downstairs funk.
But alas, as you’ve probably heard, there are cases here — dozens of them. Chalk it up to the power of headlines mentioning gross bodily functions to raise awareness about what’s been there all along.
“We’ve seen about 90 cases so far this year,” said Dr. Rachel Herlihy, the deputy chief medical officer at the Colorado Department of Public Health and Environment. “That’s really pretty close to what we see on average when you look at a five-year average.”
So why all the recent fuss, then?
From Michigan to Colorado
Well, there is an outbreak of cyclosporiasis, but it’s happening in Michigan and, possibly, surrounding states. As of Friday, Michigan’s public health department had reported 1,562 cases.
That’s not what you’ll see if you go to the Centers for Disease Control and Prevention’s page for cyclosporiasis data, though. There, in numbers lagging real-time data, the CDC reports a few hundred cases in Michigan as well as some cases in Colorado and other states. (The CDC recently scaled back a program for tracking certain foodborne illnesses, including cyclosporiasis, but it’s unclear if that has had an impact here.)
The CDC does not say that the cases on its map are connected. In fact, the agency says that the map includes “cases that have not been linked to a common source.” But reporters covering the Michigan outbreak have taken that map and — et voilà — produced headlines like “Map tracks spread of ‘explosive’ diarrhea outbreak” and “‘Explosive diarrhea parasite’ spreading across 17 states, CDC warns.”
Except that’s not how any of this works.
How cyclosporiasis actually spreads
First, the cyclospora parasite doesn’t “spread” in the way that many germs or other disease vectors do.
Herlihy said the parasite often proliferates by hitching a ride on fresh produce that’s contaminated in the field. You can get sick from eating that produce without cooking it — contaminated lettuce, for instance, is particularly tricky because you don’t cook it and washing alone doesn’t get rid of all of the cyclospora, though it does help.
Once people have shed the parasite in the aforementioned explosive ejection, it takes at least one to two weeks outside the body before the parasite becomes infectious again, according to the CDC. That severely limits its ability to hitch a new ride.
“We don’t see direct person-to-person transmission,” Herlihy said.
Hence, infection almost always occurs by eating contaminated produce or drinking contaminated water. The parasite only “spreads” as far as the dirty food and water does.
The Food and Drug Administration’s guidance to farmers acknowledges this by advising that produce growers be on the lookout for leaking septic systems and noting that wastewater systems may not always be able to rid treated water of cyclospora.
There can be sporadic outbreaks of cyclosporiasis if a bad batch of something makes it into the food supply. In 2023, for instance, Colorado saw dozens of cases of cyclosporiasis linked back to a restaurant in Ridgway.
That kind of foodborne outbreak is likely what happened in Michigan, too. And, though health officials have yet to identify the source, Taco Bell has pulled some menu ingredients from several locations as a precaution.
But none of the cases of cyclosporiasis in Colorado are tied to the outbreak in Michigan or any other state, Herlihy said.
“At this point we don’t have any cases that are part of multistate outbreak investigations,” she said.
Nor does Colorado have any local outbreaks happening.
Cases tied to international travel
So where did the illnesses here come from?
“The vast majority of cases we are seeing in Colorado are tied to food exposure during international travel,” Herlihy said.
Yes, Coloradans who pick up the bug in other countries get counted in Colorado’s case totals. (Herlihy said countries in Latin America are a common source.) This means, from a public health standpoint, there’s often not much to do about isolated cyclosporiasis cases.
“There’s no reason for us to believe that there’s an increased risk of exposure from eating produce in Colorado,” Herlihy said.
None of this is to downplay the illness, which is awful. A case of cyclosporiasis can cause watery diarrhea, painful gas, cramping and weight loss.
“It feels like someone is squeezing your insides or punching you from the inside out and trying to get out,” one Coloradan who believes she is afflicted with the parasite said in a video posted on TikTok. (She said she had recently returned from Mexico.)
The illness can last for more than a month if untreated. It can sometimes require hospitalization due to dehydration. Treatment involves prescribing antibiotics.
The other parasites for your nightmare fuel
As bad as all of this is, it’s not the most worrisome parasitic infection you can get in Colorado.
Cases of a different illness called cryptosporidiosis are more common in Colorado, with 247 having been reported so far this year. The disease causes similar symptoms to cyclosporiasis, but it can be spread person-to-person, Herlihy said. (If you want to impress at your next cocktail party, be aware that the experts often shorten these diseases to “cyclo” and “crypto.”)
Meanwhile, the giardia parasite can spread through contact with contaminated water, animals or people, making it the most common source of parasitic illness in Colorado and the United States. Last year, Colorado health authorities reported 533 cases of giardiasis, the disease caused by the parasite. That was a fairly average year.
As with many things, solid hand-washing hygiene — especially when preparing or eating food, after using the toilet or changing a diaper and after touching an animal or the soil — is a good prevention strategy.
This story previously appeared in the Colorado Sun.
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