Thousands across the United States have been affected by an ongoing outbreak of cyclosporiasis, potentially the largest in recent history.

In a recent development, Michigan health officials identified lettuce or salad greens as a possible source. They released a statement on Monday indicating that these could be linked to the outbreak. Yet, they emphasized that this finding is not definitive, and other food sources have not been excluded.

The outbreak has resulted in 2,640 reported cases in Michigan as of Monday evening, with 44 individuals hospitalized. This represents a 69 percent increase from the previous Friday’s report, reaching the highest ever annual count of infections in the state. Typically, Michigan records only about 40 to 50 cases of cyclosporiasis each year.

While Michigan reports the most cases at present, states like New York, Ohio, Illinois, Indiana, and Kentucky are also experiencing higher than usual numbers. According to the Centers for Disease Control and Prevention (CDC), at least 843 confirmed cases have been reported across 31 states, with 86 hospitalizations. However, health experts believe these numbers are likely underestimated due to reporting delays.

The New York Times has independently confirmed at least 4,800 cases this year. Since 2016, the CDC has averaged about 2,800 cases annually across the country.

Caitlin Rivers, an epidemiologist at Johns Hopkins Bloomberg School of Public Health, stated this year may set a record for cyclosporiasis cases in the United States.