Cilantro as a Suspect in Cyclosporiasis Outbreaks
The main suspect? It appears to be cilantro.
Before a wave of cyclosporiasis cases linked to iceberg lettuce hit the U.S. this summer, the New York City Health Department was already probing another smaller outbreak. Just weeks earlier, labs and physicians alerted the city that people were suffering from this parasitic intestinal illness, which can lead to severe diarrhea and other digestive troubles.
This April investigation — one of several case clusters the city has been on this year — pointed to cilantro as a potential culprit.
But, you might wonder, how do health officials track down the source of these illnesses?
City officials provided insights into the cilantro cluster. Their efforts are part of a larger national and state surveillance chain, showcasing the complexity of tracing food contamination in a global supply network. The C.D.C. is still looking into cyclosporiasis cases that are not linked to the iceberg lettuce incident.
This year alone, New York City has reported 442 cyclosporiasis cases — significantly higher than the annual average of 216 cases from 2019 to 2024.
Challenges in Tracing Cyclosporiasis
Tracking cyclosporiasis can be particularly tricky because symptoms can take up to two weeks to appear. “People might not realize that something they ate two weeks ago is what made them sick,” noted HaeNa Waechter, who leads the enteric disease team in the city’s Health Department.
Health department investigators assist individuals in piecing together their eating habits, complicated by the city’s vast number of eateries—28,000 restaurants and 17,000 food retailers. “You might shop at various markets,” Waechter explained, “so we inquire about everything to jog their memory.”
For the April cluster, the Health Department identified a common Brooklyn restaurant where everyone had dined, though they chose not to disclose its name.
Those affected seemed to have eaten guacamole or salsa, both of which usually include raw cilantro, an herb common in many Mexican dishes. Consequently, the Office of Environmental Investigations inspected the restaurant.
Investigative Procedures
“We work with the restaurant manager or food handler to conduct a step-by-step review of how those menu items are prepared,” said Joanne Casarella, who oversees food-borne illness investigations. They also spoke with the patient’s dining companions, hoping to find a control group of unaffected diners for comparison.
The investigators contacted additional diners from the restaurant’s reservation list and identified more sick individuals. Initially, between five and ten contracted the illness.
Genomic tests from the city’s Public Health Laboratory confirmed that all patients shared the same strain of cyclospora, which leads to cyclosporiasis. The Health Department sent its findings to the C.D.C., including supplier invoices for food items used at the restaurant.
“We suggested they look into the cilantro, and that initiated the traceback investigation,” shared Shama Ahuja, an assistant commissioner in the Bureau of Communicable Disease. The C.D.C. informed the city that the local cilantro supplier sourced it from a national supplier, which, in turn, received it from an international supplier. However, the C.D.C. has yet to disclose any conclusions or actions taken regarding this case.
A New Lunch Outbreak
Not long after the cilantro investigation, the city received a complaint through its 311 service: many employees at a company fell ill after a catered luncheon in Manhattan. At least 18 had tested positive for cyclosporiasis.
This investigation posed its own set of challenges because those affected had all consumed a dish containing a mixture of raw vegetables and fruits. (“It sounded delicious,” recalled Waechter.)
Investigators focused on five ingredients: cucumbers, pears, snow peas, carrots, and cilantro, sending this list and the caterer’s supplier invoices to the C.D.C. to track their origins and see if any were associated with other cases.
“We can’t be fully certain about our findings,” Ahuja remarked. “We can only relay where the data has led us.”
