Cyclospora (Cyclospora cayetanensis) is a parasite that is composed of only one cell. It is too small to be seen with the naked eye (only 8-10 microns in diameter). It is generally contracted by a person putting something in his/her mouth that was contaminated with feces. Avoiding water and food that may be contaminated with feces probably is the best way to prevent infection. Infected persons should wash their hands often to prevent the spread of infection. Persons who have previously been infected with Cyclospora can become infected again.