Summary (tl;dr)

A significant surge in cyclosporiasis, a parasitic illness causing severe gastrointestinal issues, is currently affecting multiple U.S. states, with investigations pointing towards contaminated fresh produce, particularly lettuce and salad greens, as a likely source.

Essential Background

Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis. People become infected by consuming food or water contaminated with the parasite, which is often found on fresh produce exposed to contaminated feces. Unlike many other foodborne illnesses, Cyclospora is not easily spread from person to person. Symptoms, which typically appear about a week after exposure, include frequent and watery diarrhea (often described as "explosive"), stomach cramps, bloating, nausea, fatigue, and weight loss, and can persist for weeks or even months if left untreated. Previous outbreaks in the U.S. have been linked to various raw produce items like berries, herbs, and leafy greens.

The Full Story

The United States is currently experiencing an unusually high number of cyclosporiasis cases, with state-level data suggesting that 2026 could be the nation's worst year on record for infections. Since May 1, 2026, the Centers for Disease Control and Prevention (CDC) has confirmed 1,645 domestic cases and is analyzing over 5,100 additional suspected cases across more than 30 states.

Michigan is among the hardest-hit states, reporting over 3,300 cases as of July 14, 2026. Michigan health officials have identified lettuce and salad greens as a potential source for the outbreak, based on extensive patient interviews. Neighboring Ohio has also seen a significant outbreak, with nearly 400 confirmed cases reported across 57 counties, particularly in its northwest region. Federal health officials have noted a likely epidemiological link among cases in Michigan, Ohio, Kentucky, and West Virginia, indicating a common source for these infections. Separately, Oklahoma is investigating a cluster of 57 cases, including six hospitalizations, though state officials have not yet linked these illnesses to the broader multi-state outbreak. Federal and state health agencies, including the CDC and FDA, are actively working to identify and confirm the specific food source(s) and suppliers responsible.

Why It Matters

This widespread outbreak underscores critical concerns about food safety and public health, especially concerning fresh produce often consumed raw. The debilitating symptoms of cyclosporiasis, characterized by prolonged and sometimes "explosive" diarrhea, can severely disrupt individuals' lives and may necessitate antibiotic treatment. While not typically life-threatening, severe dehydration can occur, particularly in vulnerable populations. The challenge in identifying a definitive source for the current outbreaks, partly due to the parasite's lengthy incubation period, leaves consumers uncertain about which foods to avoid. Health officials recommend thorough washing of all fresh produce under running water and, where practical, cooking items to at least 158°F (70°C) to kill the parasite, as chemical sanitizers may not be fully effective. The increasing prevalence of cyclosporiasis cases in recent years, potentially influenced by factors like climate change, highlights the ongoing need for robust surveillance and food safety measures.

Geographic Location

• Michigan, United States (widespread Cyclospora outbreak, lettuce identified as potential source)
• Ohio, United States (widespread Cyclospora outbreak, linked to multi-state outbreak)
• Kentucky, United States (Cyclospora outbreak linked to multi-state outbreak)
• West Virginia, United States (Cyclospora outbreak linked to multi-state outbreak)
• Oklahoma, United States (cluster of Cyclospora cases under investigation)