In July, Michigan experienced an unprecedented spike in cyclosporiasis, with more than 10,700 confirmed cases, a dramatic rise from the usual 50 annual cases.
The outbreak has led to over 190 hospitalizations, largely concentrated in southeastern Michigan. Oakland County alone reported more than 1,000 infections, and the majority of cases involve residents of Detroit and surrounding areas.
Young adults in their twenties to forties have been most affected, according to state health officials.
Investigations point to lettuce or other salad greens as a likely source, though no single grower or brand has been identified. Other foods have not been ruled out, and the parasite’s presence in produce remains a concern.
Health authorities recommend purchasing whole heads of lettuce, discarding outer leaves, washing inner leaves under running water, and cooking greens that can be cooked to at least 158°F (70°C). Washing alone does not guarantee removal because the parasite resists routine chemical disinfection.
A related multistate outbreak linked to shredded iceberg lettuce supplied by a Mexican producer and served at fast‑food restaurants affected nearly 2,000 people across nine states, with 98 hospitalizations.
The producer voluntarily recalled all iceberg lettuce sourced from central Mexico following positive test results confirmed in mid‑July.
Nationally, more than 6,700 cases of cyclosporiasis have been confirmed in the United States since May, with over 11,500 additional cases pending confirmation. The illness has spread to 45 states, prompting investigations into multiple food sources.
Cyclosporiasis is caused by a microscopic parasite that contaminates food or water with human feces. The parasite requires one to two weeks in the environment to become infectious, explaining why contaminated produce is the primary vehicle for transmission.
Symptoms include watery or explosive diarrhea, abdominal cramping, nausea, vomiting, fatigue, and loss of appetite. The infection can persist for weeks or recur in cycles if untreated, and treatment typically involves the antibiotic trimethoprim-sulfamethoxazole along with rest and hydration.
