The nationwide cyclospora outbreak is very likely a result of sewage contamination in the food supply, according to scientific researchers and public health officials. I am a public health water microbiologist who collects sewage water and tests it for evidence of harmful pathogens, such as cyclospora. It is not easy to measure cyclospora oocysts in sewage, contaminated water or food. There isn’t clear data on how well standard sewage treatment processes reduce the numbers of cyclospora oocysts. Across the U.S., 200 billion gallons of treated sewage wastewater are used for irrigation of agricultural lands each year.