What to know about the Cyclospora outbreak spreading across the United States

WASHINGTON: Cases of cyclosporiasis, an intestinal illness caused by the Cyclospora parasite, have risen sharply in the United States, with infections reported in 34 states, according to the US Centers for Disease Control and Prevention. The outbreak has been especially pronounced in Michigan, which first reported its surge in May and said on Tuesday that the state had recorded 3,309 cases.

The CDC said the infection is usually contracted by eating food — particularly raw fruits and vegetables — or drinking water contaminated with faeces carrying the parasite. Symptoms can vary from mild to severe and include diarrhoea, nausea and other gastrointestinal problems. Children, older adults and people with weakened immune systems face a greater risk of serious illness.

Although the illness is rarely life-threatening, untreated infections can continue for weeks and can lead to hospitalisation, particularly because of dehydration. The United States has seen Cyclospora outbreaks before. Michigan health officials said the state typically records around 40 to 50 cases a year.

Suspected source and investigation

Michigan health officials said available evidence suggests lettuce or other salad greens may be behind the current outbreak, though they said other food items have not been fully ruled out. They added that investigators have not linked the outbreak to any specific type of produce, grower or supplier.

The CDC and other state health departments have not yet identified the source of the contamination. The federal agency and the Food and Drug Administration are tracing foods reported by sick people through the supply chain, potentially back to the farm where an ingredient was grown. The investigation may also involve genetic sequencing.

Michigan officials said previous outbreaks have been associated with fresh foods including bagged salad mixes and some herbs. Past outbreaks were also linked to fresh cilantro and basil, raspberries, snow peas and green onions.

How people can reduce the risk

Health officials said the parasite is found in contaminated food or water and is not commonly spread directly from one person to another. They advised people to wash their hands with soap and water before and after preparing raw fruits and vegetables, wash produce thoroughly and scrub firm fruits and vegetables with a clean brush.

Michigan also advised consumers to buy whole heads of lettuce instead of bagged salad mixes and kits, and to discard the outer leaves. It further recommended cooking leafy greens and other items when possible.

For those infected, the CDC recommends treatment with trimethoprim-sulfamethoxazole, an antibiotic often sold as Bactrim, taken twice a day for seven to 10 days. The agency said people living with HIV may need a longer course of treatment.

Where cases are rising

The CDC said Michigan, Ohio and New York have reported particularly high numbers of infections. Illinois, Kentucky, New Jersey, New York, North Carolina and Texas had each reported 31 cases or more as of July 13.

According to the CDC, confirmed cases stood at 1,645, including 141 hospitalisations. The agency said its figures trail state reporting because of delays in submissions to the federal level, and case numbers are expected to increase as more data comes in. The period between exposure and confirmation can be as long as six weeks.

The CDC said cases usually increase between May 1 and August 31. It reported that infected people ranged in age from 5 to 88, with a median age of 44, and that 59 per cent of the cases were female.

Concerns over surveillance

The Foodborne Diseases Active Surveillance Network, or FoodNet, is a partnership involving the CDC, the US Department of Agriculture, the FDA and 10 state health departments. Last July, FoodNet stopped tracking six of eight pathogens, including Cyclospora, because of funding cuts.

Barbara Kowalcyk, director of the Institute for Food Safety and Nutrition Security at George Washington University, said FoodNet contacts physicians and clinical laboratories to monitor trends and provide context for outbreaks rather than detect them directly. She said that without Cyclospora monitoring, health officials may find it harder to understand how many cases are missed because of underdiagnosis or underreporting, and may also struggle more 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.