Since May 1st and through August 18th, the Food and Drug Administration (FDA) has confirmed over 15,000 cases of cyclosporiasis in the United States with nearly 11,000 cases attributed to a multistate outbreak from contaminated iceberg lettuce. Illnesses from such an infection can result in gastrointestinal distress lasting for up to 14 days. The number of cases confirmed this year is a significant increase from the past and highlights the necessity of robust safety protocols to protect public health and the nation’s food supply. There is currently no direct evidence of the cause of the current cyclosporiasis outbreak, but more specific information may be publicly announced in the future.
Concerns about cyclosporiasis and the absence of a direct source have raised questions for the water sector. Members of the Water Environment Federation’s Disinfection and Public Health Community have responded to these questions with a fact sheet tailored to the needs of water professionals. As detailed in the fact sheet, cyclosporiasis is caused by the parasite Cyclospora cayetanensis, and outbreaks are generally foodborne and believed to be caused by contaminated irrigation water or wash water used in the production of produce that is eaten raw.
What does this mean for water professionals?
There is currently limited data available on the fate of Cyclospora through the wastewater treatment process. There is evidence of limited removal through secondary wastewater treatment, but some commonly used disinfection practices such as chlorination are considered to be largely ineffective. However, according to the World Health Organization, filtration processes that effectively remove well-studied pathogens such as Cryptosporidium should also remove Cyclospora. Filtration removes pathogens primarily through size-exclusion, and Cyclospora is approximately twice the size of Cryptosporidium, giving credence to this assertion.
For professionals working at water resource recovery facilities, there are practical steps, identified in a 2020 Blue-Ribbon Panel, that can be taken to protect themselves from the risk of infection. The first step is proper hygiene practices such as hand washing and wearing personal protective equipment such as gloves, boots, coveralls, face shields, and safety goggles to prevent contact with wastewater. In addition, it is important for professionals to understand the limitations of chemical disinfectants, such as chlorine and other sanitizing agents, against Cyclospora and other protozoa. We encourage WEF members and the water sector to read the fact sheet to learn more.
What does this mean for water reuse?
Since contaminated agricultural irrigation water can be the cause of a cyclosporiasis outbreak, it is natural to have questions about the use of recycled municipal wastewater in agricultural irrigation. However, it is important to understand the robust safeguards and regulations currently in place for water reuse for agricultural irrigation. In the United States, water reuse is regulated by the states rather than the Environmental Protection Agency. The level of treatment and monitoring required will vary depending on the irrigation method and the type of crop being grown. Some states allow recycled water to be used in the irrigation of food crops eaten raw, including where there is direct contact with the edible portion. This method of irrigation is considered to carry the most risk. However, across the states, and internationally, these regulations are frequently the most stringent and often require filtration in addition to secondary treatment and disinfection. For example, California and Arizona are the leading producers of leafy greens and other produce like raspberries that are considered to be most at risk for Cyclospora. In both states, irrigation with recycled water for such crops is covered by the most stringent water reuse regulations they have for agricultural irrigation, with explicit requirements for filtration in addition to secondary treatment and disinfection.
Aside from state water reuse regulations, the FDA has regulations for pre-harvest agricultural water (i.e., irrigation water) quality through the Food Safety Modernization Act (FSMA). While the FSMA regulations from 2015 included microbial standards, state water reuse regulations are considered to be significantly more stringent. More specifically, according to a 2019 review of those 2015 regulations, “In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations.” It should be noted that in 2024 FDA replaced the 2015 microbial standards and testing requirements under FSMA with a systems-based approach to managing risk that cannot be easily compared to state water reuse regulations.
When considering the treatment systems in place, the regulatory safeguards associated with recycled water, the available information on the current outbreak, and the decades of history of agricultural water reuse, there is no evidence indicating that recycled water used for agricultural irrigation increases the risk of contamination by Cyclospora or other pathogens.
How can the water sector prepare for the future?
Even with no reason for immediate concern, there is still more that can be done to understand Cyclospora and how the water sector can better support public health. For example, laboratory methods for detecting and measuring Cyclospora are in need of improvement. Methods that incorporate the viability of oocysts or the identification of reliable Cyclospora surrogates could create a better understanding of the fate of Cyclospora through different treatment processes or other processing steps. Additionally, development of robust molecular methods would be invaluable for implementing wastewater surveillance initiatives that were pioneered during the COVID-19 pandemic. This would empower the public health community to better determine the scope of outbreaks and assist in deploying interventions and other initiatives.
As the public and water sector continues to have important questions about Cyclospora, WEF stands ready to respond to such questions and challenges. We will accomplish this through our global network of experts, education of the water sector workforce, and our ability to bring people together to develop solutions and build public trust, all in pursuit of a life free of water challenges.
Contact: Justin Mattingly, WEF Senior Advisor, Resource Recovery | jmattingly@wef.org
About WEF
The Water Environment Federation (WEF) is a not-for-profit, nonpartisan organization providing water professionals with the latest in education and training. WEF is leading the transformation to the Circular Water Economy: reducing waste, recovering resources, and regenerating ecosystems. Founded in 1928, WEF’s mission is to inspire its 31,000 members and 75 affiliated member organizations and the water community in pursuit of human and environmental wellbeing. WEFTEC, WEF’s premiere event, is the largest annual water quality exhibition in North America attracting a diverse, global audience. More than 20,000 registrants and 1,000 exhibitors convene at WEFTEC to experience innovative solutions and gain expert insights that positively impact the future of water. For more information, visit wef.org.