This summer the U.S. has been gripped by a parasite-borne illness that causes explosive diarrhea and has basically taken iceberg lettuce off the menu. But new U.S. Centers for Disease Control and Prevention numbers, as well as state data, suggest new infections may be tapering off.

As of August 18, the CDC had received reports of more than 15,000 lab-confirmed cyclosporiasis cases since May. That’s an increase of more than 14,000 cases compared with May 1, 2025, through August 31, 2025. Some 828 people have been hospitalized, and two people died because of the infection, according to the CDC.

There are many more thousands of yet-to-be-confirmed cases, especially considering that some states are tracking the outbreak differently than the CDC does. On Thursday in Michigan, for example, local officials said the state had seen 14,277 cases since June. And the true number nationwide may be higher still because some people who get cyclosporiasis may not have serious symptoms, meaning they are less likely to go to the doctor or get tested for the bug.

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The outbreak has been linked to iceberg lettuce, particularly lettuce produced by Taylor Farms de Mexico. The lettuce was sold at stores and at Taco Bell restaurants across the U.S. before it was recalled. Cyclosporiasis is caused by a parasite that spreads through food and water contaminated with infected human feces. The Food and Drug Administration, which oversees food safety, has said it is “confident that all recalled iceberg lettuce related to this specific Cyclospora outbreak is off the market.”

The number of new cases seems to be lessening. The CDC’s tracking data show a spike in case reports in early and mid-July, with a significant drop in new infections since then. Michigan, one of the hardest hit states, has also seen a similar tapering off of new infections in the past week or so—but they are still showing up.

It is possible that most new infections just aren’t reflected in the data yet. Cyclosporiasis symptoms can take two weeks or more to appear, and new cases are reflected in CDC data after about six weeks.

Those symptoms can include explosive, watery diarrhea, as well as fatigue and nausea. These can last anywhere from a few days to a month or longer without treatment.

To prevent an infection, the CDC recommends washing your hands and any fresh produce under running water before eating, preparing or cooking it. Cyclospora, the parasite that causes cyclosporiasis, is trickier to get rid of, though, so you need to cook any food to at least 158 degrees Fahrenheit (70 degrees Celsius) to kill the parasite. Michigan state officials said on August 6 that people can probably go back to prepping and eating salad the normal way, however.

“The broad, precautionary recommendation to avoid bagged salad mixes during the Cyclospora outbreak is no longer in effect,” the Michigan officials wrote in the August 6 announcement. “Residents may resume their usual food handling practices and make choices based on their individual risk tolerance.”

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