The epidemiology of Cyclospora cayetanensis differs in important ways from that of Cryptosporidium parvum. The oocysts of C. cayetanensis are immature when eliminated in the stool and are non-infectious, so that person-to-person spread does not occur. Most infections occur in spring and summer, probably because warm moist conditions favor maturation of the C. cayetanensis oocysts. Travelers to tropical areas are more likely than others to become infected. So far, no animal source has been identified. Fresh produce, especially imported raspberries, has been implicated in a number of epidemics, but the source of the contaminating organisms is unknown. In most instances, the produce has been imported from a tropical region. The protozoa have been identified in natural waters, but a human source could not be ruled out. Outbreaks have occurred in Canada, the United States, Nepal, Peru, Haiti, and various other countries of South and Central America, Southeast Asia, and Europe.
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