Evaluating Foodborne Cyclosporiasis Using Foodborne Diseases Active Surveillance Network and Foodborne Disease Outbreak Surveillance System Data, 2015–2019

Cyclosporiasis has been a nationally notifiable disease in the United States since 1999, and cases have increased in recent years. We evaluated characteristics of U.S. cases and outbreaks to identify gaps and potential prevention measures for mitigating cyclosporiasis. We assessed Cyclospora data from the Foodborne Diseases Active Surveillance Network (FoodNet) and from the Foodborne Disease Outbreak Surveillance System (FDOSS) collected between 2015 and 2019. There were 1,376 cyclosporiasis cases in FoodNet between 2015 and 2019. Approximately one-fifth (n = 290, 21.1%) reported recent international travel. Most cases occurred in 2018 (n = 334, 24.3%) and 2019 (n = 758, 55.1%). There was strong seasonality, with 1,160 (90.9%) cases in the summer months. Most travelers reported visiting Mexico (n = 182, 62.8%) and Guatemala (n = 25, 8.6%). Approximately two-thirds of FoodNet cases were outbreak associated (n = 987, 71.7%). Of the 79 outbreaks reported to FDOSS, 31 (39.2%) occurred in 2018 and 40 (50.6%) occurred in 2019. Outbreaks tended to occur in spring and summer months (n = 78, 98.7%), The most common age groups among the 2,335 cases with data available included 20-49 years (n = 1,168, 50.0%), 50-74 years (n = 985, 42.2%), and ≥75 years (n = 120, 5.1%). Although direct comparisons between FoodNet and FDOSS are not possible, both datasets indicate that the majority of Cyclospora transmission is domestic and not travel associated, as previously thought. These findings show the need for continued investment in Cyclospora research, including identifying populations that are underrepresented, or at higher risk for cyclosporiasis, and improved understanding of national sources and pathways of infection.