Overview
U.S. health authorities are contending with a rising number of cyclospora infections that produce diarrhea, nausea and other gastrointestinal symptoms. The U.S. Centers for Disease Control and Prevention has reported cases in 34 states. Michigan, which first reported its outbreak in May, recorded 3,309 cases on Tuesday, according to state officials.
What is cyclosporiasis?
Cyclosporiasis is an intestinal infection caused by the cyclospora parasite. The CDC says people typically acquire the parasite by consuming food - most often raw fruits and vegetables - or water that has been contaminated with feces carrying the organism. Symptoms can vary from mild to severe, and the CDC notes that children, older adults and people with weakened immune systems face a higher risk of more serious illness.
While death from cyclosporiasis is uncommon, infections that are not treated can persist for weeks and may result in hospitalization, frequently because of dehydration. The U.S. has experienced prior outbreaks of the disease; for example, Michigan officials say the state typically records 40 to 50 cases in a normal year.
Suspected sources and investigative work
Michigan health officials have pointed to lettuce or other salad greens as possible sources of the current outbreak, though they have not ruled out other food items. No specific type of produce, grower or supplier has yet been definitively linked to the illnesses.
Federal and state investigators, together with the Food and Drug Administration, are conducting traceback inquiries. They are following reports of where ill people said they ate or purchased food and are working back along supply chains to points that can extend to the farm where ingredients were grown. Genetic sequencing may be among the tools used during this trace-back process.
Michigan officials noted that prior outbreaks have been tied to fresh food items, including bagged salad mixes and certain herbs.
How individuals can reduce risk
Because the parasite survives in contaminated food and water and is not commonly transmitted directly from person to person, public health guidance focuses on food handling and preparation. Officials recommend washing hands with soap and water before and after preparing raw fruit and vegetables. Fruits and vegetables should be washed thoroughly, and firm produce should be scrubbed with a clean brush.
Michigan health authorities have advised consumers to purchase whole heads of lettuce rather than bagged salad mixes and to discard outer leaves of whole heads. They also advised cooking leafy greens and other items when feasible.
The CDC notes that past outbreaks have been associated with items such as bagged salad mixes and kits, fresh cilantro and basil, raspberries, snow peas and green onions.
Treatment
For people diagnosed with cyclosporiasis, the CDC recommends treatment with trimethoprim-sulfamethoxazole, an antibiotic commonly sold under the brand name Bactrim. The recommended regimen is twice daily for seven to 10 days. The agency adds that people living with HIV may require a longer course of treatment.
Where cases are appearing
Michigan, Ohio and New York are among the states reporting large numbers of cases. As of July 13, Illinois, Kentucky, New Jersey, New York, North Carolina and Texas had each reported 31 cases or more, according to the CDC, which tallied confirmed cases at 1,645. The agency said 141 of those people had been hospitalized.
The CDC cautioned that its figures lag behind state counts because of delays in reporting to the federal agency. Case totals are expected to rise as more data come in. The time between exposure and confirmation of a case can be as long as six weeks, the CDC said. The agency also noted that cases of cyclosporiasis typically increase during the period from May 1 through August 31.
Reported patients range in age from 5 to 88 years, with a median age of 44, and 59% of reported cases are female.
Surveillance and funding concerns
Surveillance for foodborne pathogens involves multiple federal and state partners. The Foodborne Diseases Active Surveillance Network, known as FoodNet, is a collaboration among the CDC, the U.S. Department of Agriculture, the FDA and 10 state health departments.
Last July, FoodNet stopped tracking six of eight pathogens, including cyclospora, citing funding cuts. Barbara Kowalcyk, director of the Institute for Food Safety and Nutrition Security at George Washington University, said that without monitoring for cyclospora, it will be harder for officials to understand the extent of under-diagnosis or underreporting and more difficult to prevent future outbreaks. "It’s not just FoodNet that needs funding. The whole system needs funding," she said.
The CDC did not immediately respond to a request for comment.
Practical takeaways
- Wash hands and produce thoroughly before preparation.
- Consider buying whole heads of lettuce rather than bagged mixes and discard outer leaves; cook leafy greens when possible.
- If symptoms of prolonged diarrhea and gastrointestinal illness develop, seek medical advice; the CDC recommends a specific antibiotic treatment for confirmed cyclosporiasis.
Health authorities continue tracing potential food sources and compiling case reports from states. Public health officials warn that the apparent scale of the outbreak may grow as additional lab confirmations and state reports are completed.