Cases of diarrhea caused by the parasite Cyclospora continue to rise, and with the threat of a week-long illness and uncertainty about the source, it’s easy to wonder: Is there anything in the grocery aisle that is safe to eat?
As of Thursday, one outbreak had grown to more than 4,000 cases and 102 hospitalizations in Michigan and more than 1,200 cases and 88 hospitalizations in Ohio. It is also linked to cases in West Virginia and Kentucky.
Shredded lettuce supplied by Taylor Farms and sold at some Taco Bell restaurants is linked to the outbreak, a source familiar with the investigation said Thursday. Michigan health officials previously said their investigation suggests lettuce or greens may be the culprit, but other foods cannot be ruled out.
Nationally, about 7,000 cases have been confirmed or under investigation in 34 states since May 1, the U.S. Centers for Disease Control and Prevention reported Tuesday. It is unclear whether other states are reporting cases linked to the large outbreak in the Midwest.
While Michigan health officials urge shoppers to be especially careful when purchasing and eating lettuce and greens this summer, federal health officials stress staying aware of health warnings and using standard safety precautions when washing food.
“Cyclospora is a very interesting organism. It’s a parasite, so historically it has been associated with outbreaks in the past, usually foodborne outbreaks,” said Dr. Nuwan Gunawardhana, a hospital epidemiologist and physician specializing in infectious diseases at Columbia University Medical Center in Irving.
“It’s not really thought to be contagious from person to person,” he said. “When we talk about foodborne outbreaks of Cyclospora, it is a very hardy organism, so it has the ability to stick very, very well to the surfaces of our fresh produce and fruit.”
Cyclosporiasis is an intestinal disease caused by the microscopic parasite Cyclospora, with symptoms usually developing about two days to two weeks after infection, including prolonged watery diarrhea, stomach cramps, nausea, fatigue, loss of appetite and weight loss. Although the infection can be treated with a combination antibiotic, if left untreated, the illness can last several weeks and can lead to dehydration.
Approximately 1 in every 11 cases was hospitalized. According to the CDC. No deaths were reported.
“Young children, older adults and immunocompromised people are most at risk,” said Dr. Dan Baruch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center.
“In most otherwise healthy people, the disease is often mild,” he said. “While it makes sense to take precautions, especially for people at higher risk, there is no reason to panic at this stage.”
But for people wondering what foods are safe to eat, there are a few simple steps to take both at the grocery store and at home.
When purchasing lettuce or other greens, experts recommend avoiding pre-cut or packaged produce and instead choosing whole, uncut produce, as they typically receive less handling.
Bagged salad mixes and kits have been specifically linked to previous Cyclospora outbreaks in the U.S. and Canada, Michigan health officials said.
Taco Bell said Thursday it is removing and replacing the potentially affected lettuce from restaurants in some states.
“It would probably be a good idea for now to avoid packaged salads and salad products. And if they are desired, re-wash them at home, even if they are sold pre-washed, because the actual source of the outbreak is not yet known,” Barouch said.
Raspberries, basil, salad mixes (such as vegetable trays and coleslaw), cilantro, berry and fruit mixes, lettuce and peas have all been linked to outbreaks in the past.
It is also recommended to avoid fruits and vegetables that may be bruised, damaged or moldy.
While the outbreak continues, people with weakened immune systems “may avoid eating fresh produce altogether until the culprit is identified, given that this particular population is at higher risk of severe disease,” Gunawardhana said.
But whole fruits and vegetables, including leafy greens, shouldn’t be avoided entirely, as they are still an important part of a healthy diet, says Don Stoeckel, an environmental microbiologist with the Produce Safety Alliance and a long-time fellow at Cornell’s National Good Agricultural Practices Program.
“My personal risk threshold allows me to continue to eat what I normally eat, with a little more caution when preparing it, because I know that — whatever the source of the pathogen — the vast majority of fresh fruits and vegetables on the market are safe to eat,” Stoeckel said in an email.
Michigan health officials suggest purchasing lettuce whole. It is also recommended to discard the outer two or three layers of leaves and thoroughly rinse the remaining inner leaves before use.
“If you eat foods that can be cleaned, that’s also a very optimal way to prevent ingestion of these organisms because when you clean fruits or vegetables, you’re also getting rid of contaminated surfaces,” Gunavardhana said.
Proper washing is also an important step to reduce the risk of foodborne illness, but it is not recommended to wash food with soap, bleach or commercial household cleaners as these are not food grade and may leave harmful residues.
“Stay away from soaps, detergents and other additives that are not intended for food consumption. Diluted disinfectants are not effective against protozoan pathogens such as cyclospora and may do more harm than good,” Stoeckel said.
Gunavardhana also said that chlorine is not recommended for washing.
“People think maybe chlorinated tablets will help, but actually cyclospora is very resistant to chlorine, which is another thing to be aware of,” he said.
The Centers for Disease Control and Prevention (CDC) advises: “Keep in mind that chemical disinfection or sanitization of foods may not completely eradicate cyclospora. It is important to wash foods thoroughly, even if they are labeled as having been pre-washed.”
Gunavardhana said people can take three steps to thoroughly wash products before using them:
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Wash your hands with soap and water.
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Place food under clean running water.
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Add friction by physically rubbing or scrubbing hard foods such as cucumbers, melons and potatoes with your hands or a brush.
“It won’t prevent it 100%, but it may help,” Gunavardhana said.
While washing helps reduce contamination, experts warn that it cannot guarantee complete removal of cyclospora, especially from leafy greens, herbs and delicate berries.
But washing “enhances protection when combined with cooking or cleaning,” Michigan health officials said in a news release Monday.
At a briefing Tuesday, Dr. Gwen Biggerstaff, deputy director of the CDC’s Division of Foodborne, Waterborne and Environmental Diseases, said the advice she would share with the public is what she would tell her family and friends.
“That’s my best advice: follow our ongoing food safety practices and recommendations, and stay up to date with food safety alerts and investigation updates so they know what foods are safe and know how to keep their families safe and protected,” Biggerstaff said.
It may be helpful to prioritize food preparation to reduce risk as the outbreak continues. According to the Michigan Department of Health and Human Services, cooking to an internal temperature of 158 degrees Fahrenheit or higher kills cyclospora.
Heat can kill the parasite, so cooked vegetables are less dangerous than raw foods.
“The best way to prevent illness from this particular organism is to cook it thoroughly,” Gunavardhana said. “The best way to kill this organism is to cook food to at least 70 degrees Celsius or 158 degrees Fahrenheit.”
Food safety experts also emphasize the need to prevent cross-contamination in the kitchen. Store unwashed foods separately from ready-to-eat foods and raw meat, poultry, or seafood.
“Universal advice, not just during outbreaks, is to always practice good hygiene in food preparation areas,” Stoeckel wrote.
“Maintaining clean work surfaces, including hand washing, to prevent cross-contamination from one food to another. When appropriate, cooking food (at about 160 F) kills pathogens before consumption,” he said. “Washing and, for some products, peeling will reduce the risk, but neither process will remove everything from the surface of fresh produce. Even small amounts of the pathogen when consumed can cause illness.”