Raspberries, basil, snow peas, and mesclun lettuce (all fresh, not canned or frozen) have been implicated as vehicles of infection in cyclosporiasis outbreaks in North America since the mid-1990s (Images: USDA)

People become infected with Cyclospora by ingesting sporulated oocysts, which are the infective form of the parasite. This most commonly occurs when food or water contaminated with feces is consumed. An infected person sheds unsporulated (immature, non-infective) Cyclospora oocysts in the feces, and days to weeks in the environment might be required for them to sporulate (become infective). Therefore, person-to-person transmission and transmission by eating food or drinking water that has just been contaminated with feces is unlikely to occur.

More on: Cyclospora Biology

Geographic Distribution

Cyclosporiasis occurs in many countries, but the disease seems to be most common in tropical and subtropical regions. In areas where cyclosporiasis has been studied, the risk for infection is seasonal. However, no consistent pattern with respect to environmental conditions such as temperature or rainfall has been identified.

While the disease is not known to be endemic in the United States, domestically acquired cases have been reported to CDC since the mid-1990s. To date, the fresh produce items that have been implicated in U.S. outbreaks of cyclosporiasis include fresh imported raspberries, basil, snow peas, and mesclun lettuce.

Cyclosporiasis is also reported in recent travelers to Cyclospora-endemic areas. While not everyone who travels to Cyclospora-endemic countries will become infected, travelers should take precautions, such as those recommended in CDC’s Health Information for International Travel (Yellow Book), to reduce the risk of acquiring Cyclospora and other travel-associated infections.

U.S. cases – both travel associated and domestically acquired – are reported approximately equally among males and females, and most occur in adults. Cases are reported to CDC year-round, but the majority of cases and outbreaks are reported during the spring and summer months.