Cyclosporiasis outbreak: what is gastrointestinal illness that has affected over 1,500 in the U.S.

The U.S. Centers for Disease Control and Prevention has issued a health advisory on a large cyclosporiasis outbreak in the United States. The outbreak matters because cyclosporiasis is a foodborne parasitic illness that can be underdiagnosed, can spread through contaminated produce or water, and may require multiple stool tests for confirmation.

Cyclosporiasis is caused by the microscopic parasite Cyclospora cayetanensis. Infection usually occurs through the faeco-oral route after a person consumes food or water contaminated with parasite material. The illness is not transmitted directly person-to-person.

Symptoms often begin about one week after exposure. The main feature is explosive watery diarrhoea. Other symptoms can include bloating, reduced appetite, stomach cramps, fatigue, weight loss, vomiting, and low-grade fever.

The U.S. advisory described illness in many states and said confirmed domestic infections since early May were substantially higher than in the same period of the previous year. The advisory also noted that the actual number of illnesses is likely higher than the confirmed count because cyclosporiasis is often underdiagnosed and underreported.

Cyclosporiasis can be more severe in children, older adults, and people with weakened immune systems. If untreated, the illness may persist and relapse. Reported complications include severe dehydration, malabsorption, cholecystitis, and reactive arthritis.