A mysterious outbreak of an intestinal parasite has infected thousands of people across the United States, prompting public health officials to intensify investigations to determine the source of the infection.
The number of cyclosporiasis cases in the United States has exceeded several thousand, with numbers continuing to rise and other cases under review, while Michigan alone has recorded more than 4,300 cases.
Cyclospora disease is caused by a parasite of the same name and is often linked to consuming contaminated food, especially fresh produce. The disease is not usually transmitted from person to person, as the parasite needs to go through certain stages in the environment before it can cause infection.
Symptoms of infection appear between two days and two weeks after exposure to the parasite, and include persistent watery diarrhea, stomach cramps, nausea, fatigue, loss of appetite and weight loss.
The disease can be treated with antibiotics, but without treatment, symptoms can persist for weeks and cause dehydration. Approximately one in 11 cases required hospitalization, while no deaths have been reported as a result of the outbreak so far.
Experts explained that the parasite is transmitted via fecal-oral contamination, meaning its cysts can reach crops through water or soil contaminated with the feces of an infected person. These cysts need between seven and 15 days in the environment to become infectious.
Dr. Mark Pimentel, a gastroenterologist at Cedars-Sinai Hospital, said that foodborne illnesses, such as cyclosporiasis, can affect the digestive system and cause microbiome disturbances, which may lead to some symptoms persisting for extended periods.
This parasite differs from some other foodborne pathogens in that it is not associated with farm animals; humans are its only natural host.
Investigators are now focusing on lettuce and leafy greens as potential sources of infection, after health officials in Michigan noticed lettuce repeatedly appearing in testimonies from those infected.
Although officials have assured that most agricultural products are safe, some foods are more susceptible to contamination, especially packaged salads and ready-made mixes, even those labeled "pre-washed".
Food safety expert Jason Rees said the products of greatest concern include packaged salads, fresh herbs such as coriander and basil, green onions, snow peas, leafy greens, and some types of berries.
He pointed out that cut, mixed and packaged products may be more susceptible to contamination due to the many stages of handling them, and that washing them beforehand does not mean they are free from risks, as they can be exposed to contamination during transport or storage.
Fresh herbs are among the most difficult products to clean thoroughly due to their delicate leaves, and they are often eaten raw. Parasite cysts can also cling to the rough surfaces of some fruits, such as berries, making removal even more challenging.
Doctors confirmed that washing produce with water alone may not be enough to completely eliminate the parasite, as it can stick to the surfaces of vegetables and fruits and penetrate the small cracks on them.
Health officials do not recommend completely avoiding fruits and vegetables, but rather following steps that reduce the risk of infection, and choosing products that are less susceptible to contamination.
Whole heads of lettuce are a safer option than ready-made salad mixes, provided that the outer leaves are removed and the remaining leaves are washed thoroughly under running water.
Frozen or canned fruits and vegetables are also safer alternatives, as processing methods like cooking and freezing help eliminate the parasite. Cooked vegetables remain the safest option, as heat kills the parasite at high temperatures.
Some fruits and vegetables with peels, such as bananas, avocados, oranges, melons, cucumbers, and pineapples, offer natural protection, provided the peel is washed thoroughly before cutting. Peeling some vegetables and fruits, such as carrots, potatoes, and apples, also helps reduce the risk of contamination.
Experts advise washing fruits and vegetables under running water before eating them, even if they look clean, and separating the leaves in fresh herbs and washing them thoroughly.
Soap or bleach should not be used to clean food products, and vinegar, baking soda, or soaking in salt water has not proven to be more effective than running water in removing the parasite.
Experts warn of cross-contamination within the kitchen, calling for the use of clean cutting boards and utensils when preparing fruits and vegetables, and keeping them away from raw meat, poultry and seafood.
Hand hygiene and disinfecting kitchen surfaces remain among the most important measures to reduce the spread of infection.
