Health officials find source of diarrhea-inducing parasite in WA. Here’s what to know
Health officials now have a clear answer about the origin of cyclosporiasis cases across Washington state and the nation.
It’s being driven by contaminated lettuce and salad greens, according to the U.S. Centers for Disease Control and Prevention.
The CDC and state health departments, including Michigan’s Department of Health and Human Services have moved from identifying a “potential source” to a more definitive link, pointing directly to leafy greens as the primary vehicle for the Cyclospora parasite.
However, officials say other foods cannot be ruled out, and there’s been no specific type, grower or supplier identified as the source for contaminated lettuce.
What Is cyclosporiasis?
Cyclosporiasis is an intestinal infection caused by the protozoan parasite Cyclospora.
Cyclosporiasis is contracted after consuming foods or water contaminated by the microscopic parasite, according to the U.S. Food and Drug Administration.
“Case counts typically rise during spring and summer months,” the CDC said, noting that May 1 to Aug. 31 is considered the annual cyclosporiasis season.
What are symptoms of Cyclospora infection?
Symptoms typically begin about one week after exposure and can persist for weeks without treatment, health officials say.
The Cyclospora parasite causes “watery, and sometimes explosive, diarrhea and other stomach problems,” according to the Cleveland Clinic.
Other common symptoms include:
- Loss of appetite
- Bloating, including burping and farting
- Extreme tiredness (fatigue)
- Low-grade fever
- Stomach cramps
- Nausea
- Vomiting
How many cases have been confirmed in the US?
Since May 1, the CDC has received reports of at least 1,645 confirmed cases of cyclosporiasis in the United States, resulting in 140-plus hospitalizations,
The federal health agency said it is “aware of more than 5,100 cases that require further analysis to confirm the illness as domestically acquired cyclosporiasis.”
A total of 34 states have reported Cyclospora infections since May 1, according to the CDC.
Based on past trends, federal health experts expect case numbers to continue to rise.
What about Washington state?
Washington state has reported a total of 27 provisional cases of cyclosporiasis since May 1, according to Mark Johnson, public information officer for the Washington State Department of Health.
Of those, 22 cases involved international travel to an endemic area, Johnson said, while three cases were “acquired domestically.”
There were two cases where “international travel status is unknown,” according to state health officials.
“None of these cases are associated with outbreaks in other states,” Johnson wrote in an email to McClatchy Media. “Washington state does not have a cyclosporiasis outbreak.”
As of Tuesday, there had been no confirmed hospitalizations in Washington state due to cyclosporiasis, Johnson said, and no deaths linked to the parasitic infections.
Are there any cases in Pierce County?
As of early July, one cyclosporiasis case had been reported in Pierce County, The News Tribune previously reported.
“We have had one case of cyclosporiasis in Pierce County this year, reported on July 1 and associated with international travel,” Tacoma-Pierce County Health Department media representative Kenny Via told The News Tribune.
According to the state Health Department, zero to 11 cyclosporiasis cases are typically reported each year, “mainly after international travel.”
Lettuce and salad identified as outbreak culprits
Michigan health officials, which are at the center of a large multistate outbreak in the Midwest, have identified the source of the cyclosporiasis outbreak in their state.
New epidemiological data and traceback investigations have led to leafy greens as the most consistent exposure among affected individuals.
Public health messaging has shifted from “consider other foods” to “avoid or properly handle raw leafy greens,” indicating that the evidence now points decisively to lettuce and related products.
How to prevent getting sick
The FDA recommends following these steps to stay safe during Cyclospora season:
- Discard outer layers of fruits and vegetables
- Rinse all fresh fruits and vegetables under clean running water.
- Use a clean vegetable brush to scrub firm produce.
- Be cautious with pre-washed or pre-cut produce.
- Clean kitchen counter tops, cutting boards and utensils with hot, soapy water.
- Cook produce to a temperature of at least 158 degrees.
You should always wash your hands with warm water and soap for at least 20 seconds before and after handling food, the FDA said.
This story was originally published July 16, 2026 at 9:15 AM with the headline "Health officials find source of diarrhea-inducing parasite in WA. Here’s what to know."