Amid Cyclospora Outbreak, Needham Experts Weigh in

July 17, 2026
• Local medical and public health experts shared information on the causes and signs of the illness and preventative measures residents can take to avoid infection.

Bagged salads, fresh herbs and dense, crannied produce — such as broccoli and raspberries — may be off the menu for a few weeks.

Cyclospora, an intestinal parasite that causes watery diarrhea and abdominal cramping, is commonly linked to such food amid an ongoing nationwide outbreak. While the midwest is seeing a greater surge in infection, particularly in Michigan, there have been about 30 cases in Massachusetts this year as of July 13, according to the Massachusetts Department of Public Health.

The illness is seasonal, with the vast majority of cases occurring between May and September, town Epidemiologist Emily Conners said. Typically, the state has seen an average of 85 cases per year since 2023.

Loss of appetite, fatigue, bloating and nausea are all hallmark symptoms of cyclosporiasis, which can result in dehydration, weight loss and imbalances in electrolytes, Conners said. But those symptoms can resemble other gastrointestinal and foodborne illnesses, making it perhaps harder to diagnose. There are, however, distinguishing features: the illness’s late onset, as well as its course.

“The incubation period is somewhat long for cyclosporiasis, so you can eat something that’s contaminated with the parasite and not experience any symptoms for a few days or even a few weeks, so it does make it fairly hard to trace back what is causing the outbreak,” Conners said. “Another interesting thing about this condition is it’s a little different from other diarrheal conditions in that it kind of waxes and wanes, so you can start to feel better, and then your symptoms might come back after a few days.”

Diarrhea lasting longer than 24 hours is a telltale sign of cyclosporiasis, said Dr. Matthew Lee, medical director of infectious diseases at Beth Israel Deaconess Hospital – Needham.

Medical experts advise people to exercise caution with pre-made salad kits, as those have been linked to cyclospora, Lee said, but if people do buy them, it’s recommended they thoroughly rinse them under cold water. For vegetables with layers, such as lettuce, current guidance suggests that people peel back and discard the outer layers and just use the inside, Lee added.

“I’m very cautious about giving a blanket recommendation to avoid all lettuce and leafy greens,” he said. “In terms of all foodborne illnesses, for fresh produce or vegetables, consideration could also be paid for cooking those as well, because the heat will kill a lot of bacteria and parasites.”

Parasites die when cooked at at least 158 degrees, Needham Public Health Nurse Ginnie Chacon-Lopez said, but cooking a salad “sounds disgusting.”

“It’s harder to kill it off of fresh produce if your idea is to have a salad,” she said, “but probably the best way to kill it off right now is to cook it off, and freezing doesn’t work either.”

Fresh herbs, such as basil and cilantro, as well as onions, snap peas and snow peas have all been linked to cyclospora in the past, Chacon-Lopez said. Produce from smaller farming operations is deemed slightly safer, but not definitively so, she added.

For smooth fruits and vegetables you cut into — think watermelon and cucumbers — Conners said it’s important to still wash the outside, as the unwashed skin could contaminate the inside.

Physicians diagnose cyclospora illness in two ways. More commonly, the illness is detected through a direct microscopic examination of stool, where the egg cells of cyclospora are visible, Lee said. The parasite can also be traced through molecular-based methods, wherein experts look for the DNA of the organisms, Lee said.

Treatment involves a common antibiotic, abbreviated TMP/SMX.

Unlike related illnesses, cyclosporiasis cases are still relatively low, he added.

“I think it’s important to know that every year, we do see reported cases in Massachusetts, but in the past, it tended to be a less frequent cause of diarrhoeal illness compared to other infections like norovirus, salmonella and campylobacter,” Lee said.

About half of those in Massachusetts diagnosed cyclosporiasis reported traveling out of state in the last two weeks, Conners said, referring to state data. Cases will likely rise as more people are tested, as they did with Covid.

“I think people are just getting a little bit more aware of their symptoms, so I think they’re more likely to go get seen and diagnosed,” Chacon-Lopez said.

Lee said he expects to see increased testing that could capture more cyclospora cases than in years past.

“I think the real question will be comparing that to last year and the years before, and is that really a significant increase above last year’s? I think it’s too early to say right now, until we see more numbers of identified cases,” Lee said. “I know the DPH on the back end will also investigate those to see what are the links in those situations as well.”

The surge in cases comes after cuts to FoodNet, a federal program that tracks data on microbes. FoodNet previously surveilled cyclospora but stopped doing so in 2025.

Despite some severe symptoms, the parasitic infection is non-life-threatening and rarely results in hospitalization. Of the nearly 7,000 suspected and confirmed cases in the country, about 141 people have been hospitalized and none have died. Those with weakened immune systems can be more susceptible to extreme illness, according to the U.S. Food and Drug Administration. The exact source of the parasite is unclear.

For those experiencing symptoms consistent with cyclosporiasis, it’s best to be “on the safe side” and contact your physician, Conners said.

“If you’re experiencing watery diarrhea for a handful of days, I think it’s valid at this point in time to seek medical attention,” she said. “And then obviously, if you are experiencing these symptoms and you’re getting very dehydrated, dizzy when you’re standing up, your heart rate is increased, definitely [seek] medical attention urgently.”