Federal health officials added 1,821 laboratory-confirmed Cyclospora cases to the national count in a single weekly update, bringing the domestic total to 15,716 since the season opened on May 1. The figures come from the CDC cyclosporiasis surveillance page, which was reviewed and republished on August 18 with data current through August 17. The previous posting, which covered data through August 10, listed 13,895 cases.
Hospitalizations rose to 828, an increase of 88 from the previous posting, and the agency continues to list two deaths, both reported in Michigan. Cases have now been reported by 47 states, the District of Columbia, and Puerto Rico.
The number that changes the practical picture for households is not the confirmed total. CDC also reported that it is aware of at least 11,841 additional cases that are either not laboratory-confirmed or still require investigation to determine whether they were acquired inside the United States. That backlog grew by roughly 1,400 in the same week, which means the confirmed national figure is a floor rather than a ceiling.
The Week's Increase Does Not Describe This Week's Illnesses
A jump of 1,821 cases in seven days is not a record of 1,821 people falling ill during those seven days. CDC has cited a lag of roughly six weeks between when a person becomes sick and when the case is reported to national surveillance. Stool testing must be specifically ordered; laboratories confirm the parasite, and state and local health departments then report the case through the national notifiable disease system.
The median illness onset date in the current domestic series is July 7, with the range running from May 1 through August 13. That median is the more reliable indicator of where transmission actually sat, and it points to early July rather than mid-August.
MedicalDaily previously reported on why case counts keep climbing after transmission slows, and that dynamic explains most of what readers will see between now and the fall. The official season closes on August 31, but illnesses occurring in the final days of the season will not appear in national figures for weeks afterward.
The Scale Against Last Year
The comparison CDC publishes on its own page is the clearest measure of how unusual this season has been. Between May 1 and August 31 of 2025, the agency recorded 1,180 domestically acquired cases. The current count has passed 15,716 with two weeks of the season still to run.
CDC attributes much of the increase to a large multistate outbreak linked to processed iceberg lettuce grown in central Mexico, stating that the outbreak "has contributed significantly to the increase in Cyclospora cases this year." The CDC outbreak page for the lettuce investigation puts that cluster at 9,481 cases, 398 hospitalizations, and two deaths across 17 states in data posted on August 13, and the FDA investigation of the multistate outbreak tracks the traceback. The lettuce was recalled in mid-July under a Taylor Fresh Foods recall notice covering all iceberg lettuce sourced from central Mexico by Taylor Farms de Mexico.
The lettuce does not explain everything. CDC said it and the FDA are investigating at least six additional clusters for which sources have not been confirmed. For consumers, that is the uncomfortable part of the picture, because an unidentified source cannot be avoided by checking a label.
Patients in the domestic series ranged in age from 1 to 99, with a median age of 46, and 57 percent were female. A separate group of 1,681 laboratory-confirmed cases involved people who became ill after traveling outside the country, with 61 hospitalizations and no deaths.
Households Face a Testing Problem, Not a Contact Problem
Cyclospora does not spread from person to person. A sick household member is not contagious to the rest of the family. What a household shares is an exposure history, and that is the detail worth mentioning to a clinician.
The diagnostic gap remains the single most fixable obstacle. A routine stool examination, the default test when someone reports diarrhea, does not reliably detect this parasite. CDC advises that testing has to be requested specifically, and its clinical care guidance covers both diagnosis and treatment. That requirement is a major reason the confirmed count and the true burden diverge so widely.
State health departments sometimes publish higher figures than those shown in the federal table. CDC says both can be correct, because states may count cases that do not meet the federal laboratory-confirmed reporting criteria.
People at higher risk of a difficult course include older adults, people who are pregnant, and anyone whose immune system is suppressed by illness or medication. Untreated infection can last for weeks and often improves only to return, a pattern that leads people to assume they have recovered.
Steps Worth Taking in the Season's Final Weeks
Anyone with watery diarrhea lasting more than a few days, particularly diarrhea that eases and then comes back, should contact a clinician and ask whether testing for Cyclospora is appropriate. Effective treatment is available. Local health departments can point uninsured patients toward lower-cost options.
Signs that warrant prompt evaluation rather than watchful waiting include markedly reduced urination, dizziness upon standing, inability to keep fluids down, confusion, or significant unintentional weight loss. This article is general information and is not a diagnosis.
The recalled iceberg lettuce is no longer a live risk, since the best-by dates on the affected product have passed and it should no longer be in stores or restaurants. Washing produce lowers risk but cannot guarantee removal of Cyclospora, according to the CDC, which notes that cooking produce to at least 158 degrees Fahrenheit kills the parasite. CDC issued a health alert network notice to clinicians about the season in mid-July.
CDC updates the surveillance page weekly. The next posting is the item to watch, along with whether the FDA names a source for any of the unresolved clusters.
Key Questions Answered
What is the newest confirmed national number? CDC reported 15,716 laboratory-confirmed domestically acquired cases, 828 hospitalizations, and two deaths, with data current through August 17 and published August 18.
Does the weekly increase mean cases are accelerating now? Not necessarily. CDC has cited a lag of roughly six weeks between illness onset and national reporting, so most of the newly added cases reflect illnesses that began weeks earlier. The median onset date in the series is July 7.
How does this compare with last year? CDC recorded 1,180 domestic cases between May 1 and August 31 of 2025. The current season has passed 15,716, with two weeks remaining.
What are the 11,841 additional cases? Cases CDC is aware of that are not yet laboratory-confirmed, or that require further investigation to determine whether they were acquired in the United States.
Is the recalled lettuce still a danger? No. The best-by dates on the recalled product have passed, and it should no longer be in stores or restaurants. Other clusters remain under investigation with no source named.
Can it spread between family members? No. Cyclospora spreads through contaminated food or water, not from person to person.
When should someone call a doctor? Watery diarrhea lasting more than a few days, especially if it improves and returns, along with cramping, bloating, nausea, appetite loss, or fatigue. Severe dehydration warrants urgent care.
