Aug. 20, 2026, 4:10 p.m. ET
Cases of cyclosporiasis, a parasitic infection known for causing explosive diarrhea, appeared to be slowing as federal health officials continue investigating unprecedented outbreaks of the illness across 47 states.
The Centers for Disease Control and Prevention said in a weekly update on Aug. 18 that 15,716 cyclospora infections have been confirmed across 47 states plus Washington, DC, since May 1 – an uptick of 1,821 since its last report on Aug. 11. While these numbers show that confirmed cases themselves are still rising, the overall trend is on a downward swing; previous weeks regularly saw increase that numbered into the 2,000 and 3,000 range.
There have been two deaths and 828 hospitalizations, 88 of which were reported since last week.
At least 11,841 additional cases have not yet been confirmed by laboratories, the CDC said. The agency’s case count lags about six weeks behind state-by-state numbers due to the process required to confirm and officially report an infection back to the federal level.
Michigan, which has been at the center of the largest case cluster, reported 14,277 total cases as of Aug. 20, up from 13,909 on Aug. 11. The state’s health department previously said in an Aug. 6 notice that the pace of new case reports and related emergency department visits was slowing and that residents could resume normal lettuce-eating habits. Some experts told USA TODAY, however, that caution may still be prudent in the produce aisle.
“If you’re really thinking about keeping your family safe, it’s not unreasonable to continue to wash your lettuce at this time while we watch the numbers go down,” said Dr. Sharon Nachman, chief of the Division of Pediatric Infectious Disease at Stony Brook Children’s Hospital.
See map of states with cyclosporiasis cases
Only three states, Delaware, Hawaii and New Mexico, do not have federally confirmed cases. Michigan and Ohio remain the two states hit the hardest.
The CDC reports only lab-confirmed cases that occurred on or after May 1 in people who did not travel internationally within 14 days of illness onset. Its numbers often lag behind those cited by state health officials because of tracking, verification and reporting processes. There’s typically a six-week reporting lag between an illness and the case being reported to the CDC.
What is cyclosporiasis? What are the symptoms?
Cyclosporiasis is a parasitic infection that causes gastrointestinal symptoms often associated with food poisoning, such as diarrhea, nausea and vomiting. It is caused by the parasite Cyclospora cayetanensis, also known simply as cyclospora, and is usually contracted through contaminated food or water.
Though unpleasant, it is not generally known to cause death, and in many cases it goes unreported because people recover at home without visiting a doctor. It can cause more serious complications in people with compromised immune systems or other underlying health problems.
The most common symptom is watery, frequent and sometimes “explosive” diarrhea that can go away and come back, according to the CDC and Cleveland Clinic, though other troubles can include:
- Vomiting
- Loss of appetite
- Bloating, including burping and gas, or stomach cramps
- Extreme tiredness (fatigue)
- Fever
- Nausea
Largest outbreak linked to lettuce hits 17 states
While the CDC is currently investigating multiple separate clusters of the gastrointestinal illness, only one source has been identified so far. It is unlikely that there is one common cause behind all the outbreaks nationwide, according to the CDC.
The largest outbreak, centered in Michigan, was tracked by the Food and Drug Administration back to recalled iceberg lettuce grown by produce giant Taylor Farms in central Mexico. This specific set of illnesses, first identified through traceback from fast-food chain Taco Bell, accounted for 9,481 cases and 398 hospitalizations across 17 states as of Aug. 13, per the CDC.
These states were identified after health officials interviewed and tested sick people to determine whether their infections were related. Those that are related are considered part of the same outbreak, likely stemming from the same source. Thus far, these states are the only ones the CDC has confirmed as having cases related to each other and the lettuce.
Both deaths that have occurred in the outbreak were associated with the lettuce-linked outbreak, according to the agency.
The source of a cyclosporiasis outbreak is more difficult to track than foodborne illnesses because of a long incubation period, difficulty obtaining samples and the inability to use the same genetic tracking tools available for pathogens like E. coli and listeria.
Some experts have also pointed to cuts to federal food and disease monitoring programs, though Health and Human Services Secretary Robert F. Kennedy Jr. has disputed these critiques.