More than 400 people across 18 states have been infected with cyclospora, a parasite that is transmitted through food and water contaminated with feces and causes stomach cramps, nausea, vomiting and severe diarrhea. At least 20 people have been hospitalized, according to the Centers for Disease Control and Prevention, and no deaths have been reported.
New York, Texas, Illinois and Michigan have the most cases so far, according to the C.D.C. and state health officials.
Cyclosporiasis, the disease caused by the parasite, is most common during the spring and summer months — when people are eating a lot of fresh produce like basil, cilantro, spinach and berries, which have been implicated in past outbreaks. The latest illnesses have sparked alarm, since case numbers are unusually high and have no identified source.
The C.D.C., which tracks infectious diseases, reported on July 1 that there had been 145 cases across 17 states from May 1 through June 16 that did not involve travel outside the country. But the agency acknowledged that there were now probably more cases throughout the United States. Michigan, which was not among the 17 states the C.D.C. included in its latest figures, reported more than 300 cases on Thursday.
Typically, Michigan reports only 50 cases per year, said Dr. Teena Chopra, a professor of medicine at the Wayne State University School of Medicine. And even Michigan’s latest figures are most likely an undercount, she said, since many people who are sick don’t go to the doctor and get tested for the disease. “This is the tip of the iceberg,” Dr. Chopra said.
Health officials in New York City said that there were about twice as many cases reported from January through June of this year as in the same time period last year.
C.D.C. officials were not available for an interview on Thursday, but the agency said via email that there was no evidence that the outbreaks across the country were emanating from a common source.
Dr. Luis Marcos, a professor of medicine and infectious disease physician at Stony Brook Medicine in New York, said that public health investigations in the past had traced outbreaks back to a single source, such as a large batch of produce that was distributed in the region or nationwide. A 2022 Florida outbreak was linked in part to bagged romaine lettuce in a Caesar salad kit.
If the culprit is identified, Dr. Marcos said, “we’ll know what not to eat.”
But identifying the source can be difficult because it can take about a week for symptoms to show up after an infection, and people often have difficulty remembering exactly what they ate, Dr. Chopra said.
Symptoms of cyclosporiasis include cramps, nausea, loss of appetite, vomiting, fatigue, body aches, low-grade fever and other flulike symptoms. While those who are healthy can clear the illness without treatment in days or weeks, vulnerable people like young children, older adults and those who are immunocompromised can become dehydrated and develop complications requiring hospitalization. The disease can be treated with antibiotics.
The C.D.C. advises people to protect themselves by following general hygiene and food safety practices. Wash your hands with soap and water before and after handling fresh produce, and wash fresh produce thoroughly with fresh water before eating it. Scrubbing firm fruit and vegetables with a produce brush and cutting away bruised or damaged areas also helps remove contaminants.
Those experiencing vomiting and diarrhea should drink plenty of water and other fluids to avoid dehydration.
The disease is generally not transmitted from person to person.
Joseph Goldstein contributed reporting.
