Michigan on Thursday reported 13,909 cases linked to an outbreak of cyclosporiasis, an increase of roughly 11% from last week, as the state continued to account for the bulk of cases in the multi-state outbreak of the parasitic illness.
The outbreak has shaken people across the United States, raising concerns about eating fresh produce and going to restaurants, in addition to causing illness.
Despite a weekly jump in cases, Michigan health officials said new cyclosporiasis case reports and related emergency department visits were declining, adding that residents could resume routine guidance for consuming lettuce and salad greens. The department had last week said new case reports appeared to be slowing.
Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota, said he believes the latest cases are not evidence of ongoing transmission but reflect the fact that the state had a backlog in testing.
Some Michigan health systems last month reported significant delays in the reporting of test results as the high volume of cases resulted in a shortage of test kits and reagents.
Corewell Health, a non-profit chain of 21 hospitals across Michigan, issued guidance on July 22 saying that due to the current outbreak, it would take 8-21 days to deliver test results, up from the normal 2-4 day wait time.
With these new cases, Osterholm said, it is important to understand when symptoms first emerged, details the state has not provided.
Michigan previously reported two deaths associated with the outbreak, with officials saying both individuals had significant underlying health conditions.
Wayne County had the highest number of cases at 1,794, followed by Oakland County with 1,344. People aged 30 to 39 accounted for the largest number of cases by age group, with 2,615 infections. The state health department said 314 of those infected were hospitalized.
The outbreak, which has been linked to iceberg lettuce sourced from privately held Taylor Farms operations in central Mexico, has shaken consumer confidence in lettuce and other fresh produce.
U.S. producer prices for lettuce plunged 73% in July from a month earlier, the steepest decline in more than two decades, Labor Department data showed on Thursday.
The July collapse reversed sharp price gains recorded in May and June and coincided with a sharp drop in consumer demand for lettuce and menu items containing leafy greens, the data showed. Lettuce producer prices were also down 50.1% from a year earlier.
"Cases may be declining, but not necessarily very quickly because once an outbreak is announced, older cases often start getting reported," said Martin Wiedmann, Gellert Family Professor in Food Safety at Cornell University.
"There is a significant lag between when someone consumes contaminated food and when illness is detected and reported," Wiedmann noted. "I'm not sure I would have advised people not to eat lettuce when the warning was first issued."
The fallout has also spread to restaurants, with Taco Bell owner Yum Brands (YUM.N) and Chipotle Mexican Grill (CMG.N) reporting pressure as diners grew more cautious about ordering menu items containing leafy greens.
The U.S. Centers for Disease Control and Prevention has reported 13,895 laboratory-confirmed cyclosporiasis cases across 47 states in the United States, as of August 11.
Acting U.S. FDA Commissioner Kyle Diamantas said Americans should remain confident in the safety of fresh produce after the agency finalized guidance on produce preparation and packaging in an effort to counter persistent foodborne outbreaks.
