Overview
Federal and state public health authorities are engaged in a large-scale inquiry into a surge of intestinal infections caused by the cyclospora parasite. The Food and Drug Administration (FDA), the Centers for Disease Control and Prevention (CDC) and dozens of state health departments are investigating an outbreak that public health officials say is among the largest U.S. cyclosporiasis events in recent years.
What authorities have reported so far
Michigan has reported more than 10,000 cases and is probing potential sources beyond the initial cluster associated with lettuce. The CDC has published figures showing 6,707 laboratory-confirmed cases of cyclosporiasis across 45 states, and 423 of those patients had required hospitalization. Health officials caution that those numbers likely understate the full scale of illness because it can take up to six weeks to determine whether an individual case is part of the outbreak.
Link to restaurant-served shredded lettuce
Traceback work by the FDA has connected thousands of illnesses to shredded iceberg lettuce that was served at Taco Bell restaurants across nine states. Those states include Indiana, Kentucky, Michigan, Ohio, West Virginia, Illinois, Kansas, Oklahoma and Pennsylvania. The traceback points to iceberg lettuce processed by Taylor Farms and sold in shredded form to the restaurant chain.
The FDA initially reported on July 18 that laboratory testing had found cyclospora in a sample of shredded iceberg lettuce supplied by Taylor Farms, but the agency withdrew that specific positive result a day later after a laboratory review determined the test result was a false positive. Despite that reversal, the FDA's ongoing inquiries continue to implicate Taylor Farms. The company subsequently initiated a voluntary recall of iceberg lettuce sourced from central Mexico and halted operations at its processing plant in that region.
The recall covered multiple products, including Marketside-branded lettuce sold by Walmart and dozens of items distributed through Sysco and other food distribution companies, according to the FDA. Taylor Farms issued a statement on July 24 saying the recall was voluntary and asserting that it maintains "best-in-class" cyclospora prevention protocols. The company also said it has stopped sourcing iceberg lettuce from the affected region.
About cyclosporiasis
Cyclospora infection, or cyclosporiasis, is caused by consuming food or water contaminated with feces that carry the cyclospora parasite. Fresh fruits and vegetables are the common vehicles for transmission. Symptoms can range from mild to severe. Children, older adults and people with weakened immune systems face higher risk of more serious illness.
While cyclosporiasis is not generally considered fatal, infections that are not treated can persist for weeks and may cause dehydration severe enough to require hospitalization. The CDC identifies May 1 through August 31 as the annual cyclosporiasis season in the United States.
The United States has experienced prior cyclospora outbreaks linked to fresh produce. The CDC noted a multistate outbreak in 2020 associated with bagged salads that sickened nearly 700 people across 13 states.
Prevention and consumer guidance
The FDA advises that the most reliable way to kill cyclospora on produce is to apply heat - specifically, cooking produce to at least 158 degrees Fahrenheit (70 degrees Celsius). Routine chemical disinfection methods commonly used in household or commercial settings are generally ineffective against the parasite. The agency also recommends discarding outer leaves of leafy vegetables and rinsing fruits and vegetables thoroughly before peeling or eating them.
Authorities note that cyclospora most often spreads through contaminated food or water and is not commonly transmitted directly from person to person.
Treatment
The CDC recommends treatment with the antibiotic combination trimethoprim-sulfamethoxazole, commonly known by the brand name Bactrim, taken twice daily for seven to 10 days for those diagnosed with cyclosporiasis. The agency indicates that people living with HIV may need longer courses of treatment.
Surveillance and reporting
Cyclospora is a nationally notifiable pathogen. Many states maintain robust surveillance systems and routinely share data with the CDC. Gwen Biggerstaff, deputy director of the CDC's Division of Foodborne, Waterborne and Environmental Diseases, has emphasized that most states collect and report strong data to the national surveillance system.
Healthcare providers are legally required to report cyclosporiasis cases to public health departments in 47 states. The Foodborne Diseases Active Surveillance Network, known as FoodNet, is a collaboration among the CDC, the U.S. Department of Agriculture, the FDA and 10 state health departments intended to monitor trends over time. Last July, FoodNet stopped tracking six of eight pathogens, including cyclospora, due to funding reductions. Officials say FoodNet's activities are designed to identify long-term trends and do not replace national surveillance, and participating states continue to report cyclospora cases on a national basis in the same manner as previous outbreaks.
Ongoing work and limitations
Investigations remain under way into other potential sources of contamination beyond the shredded iceberg lettuce identified in the Taco Bell traceback. Public health officials are continuing laboratory testing, data collection and supply-chain analysis as they seek to identify links and limit further illness. At the same time, the lag between illness onset and confirmation means that counts of outbreak-associated cases may rise in the coming weeks as more laboratory results are reported.
For further guidance, consumers and clinicians should follow directives from their local public health departments and consult CDC and FDA updates as investigators continue their work.