Epidemiology & Risk Factors
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. The oocysts are thought to require at least 1–2 weeks in favorable environmental conditions to sporulate and become infective. Therefore, direct person-to-person transmission is unlikely, as is transmission via ingestion of newly contaminated food or water.
Cyclosporiasis occurs in many countries, but it 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 has been identified regarding the time of year or the environmental conditions, such as temperature or rainfall.
In the United States, foodborne outbreaks of cyclosporiasis have been linked to various types of imported fresh produce, such as raspberries, basil, snow peas, mesclun lettuce, and cilantro; no commercially frozen or canned produce has been implicated to date.
U.S. cases of infection also have occurred in persons who traveled to Cyclospora-endemic areas. To reduce the risk for infection, travelers should take precautions, such as those recommended in CDC’s Health Information for International Travel (Yellow Book). Travelers should be aware that treatment of water or food by routine chemical disinfection or sanitizing methods is unlikely to kill Cyclospora oocysts.