A parasite in bagged salad was linked to a spike in cases of a stomach bug that can cause explosive diarrhea

• A doubling of stomach illnesses in Florida was linked to a parasite. 
• Cyclosporiasis can cause explosive diarrhea, but usually goes away on its own.
• Leafy greens like salad are among the leading causes of food poisoning in the US.

A doubling in cases of a stomach illness in Florida last year was partly linked to people eating bagged salad containing a parasite, according to the Centers for Disease Control and Prevention.

The illness, cyclosporiasis, is caused by a microscopic parasite called Cyclospora cayetanensis, which can spread to humans from food and water contaminated with feces carrying it. In the US, cases are often linked to people ingesting imported fresh produce carrying the parasite, according to the CDC. However, cases have recently been linked to US-grown produce.

There were 513 confirmed cases of cyclosporiasis in Florida in 2022, double the amount reported the previous year, according to a CDC report published on Thursday. The Florida Department of Health surveyed 457 of these people to find out how they were exposed to the parasite.

Of those, 330 hadn't travelled internationally, including 200 who had been exposed to prewashed bagged salad in the weeks before they became ill the in spring and summer of 2022. A further 85 of those 200 people (43%) had eaten the same brand of Caesar salad kit from the same grocery store chain, which contained only romaine lettuce. 

Genetic testing of stool samples from 211 of the cyclosporiasis patients also traced the illnesses back to bagged salad, but the source of the contamination was not discovered. 

Cyclosporiasis can cause diarrhea, stomach pain, and nausea

Symptoms of cyclosporiasis include watery diarrhea and sometimes explosive bowel movements, as well as loss of appetite, bloating, stomach pain, nausea, and fatigue, according to the CDC. 

The illness can go away by itself in people with healthy immune systems, which can take between a few days to a month if left untreated. Doctors can also prescribe antibiotics to treat the illness, and antidiarrheal medicine can help to lessen the symptoms.

Leafy greens are a common cause of food poisoning

Most bagged salads are safe to eat, but a 2018 CDC study found that between 1998 and 2008, leafy vegetables were the type of produce most likely to cause illness.

This is because there are so many points at which fresh produce can become contaminated before it reaches your plate – including germs from animal poop getting into the water used to keep plants hydrated, in the processing and transportation of the produce, and from unwashed hands picking produce up in grocery stores.

Leafy greens also spoil quicker than other foods, so can go bad even before they are technically out of date. Unlike other foods, they are risky to consume after their use-by date.

You can prevent cyclosporiasis by washing your fresh produce

Anyone can get sick with cyclospoiasis, but handling fresh fruit and vegetables correctly can help prevent it from spreading. This means washing all fresh produce before eating or cooking with it, and refrigerating cut, peeled or cooked produce as soon as possible, the CDC says. 

The US government's FoodKeeper App recommends that you refrigerate bagged leafy greens and consume them within two days of opening.