Michigan officials looked at 190 food exposures from Taco Bell and found that 90% of the people admitted to eating iceberg lettuce from one of the restaurants. Then Michigan informed the Centers for Disease Control and Prevention (CDC) of its findings. The CDC then examined data from 1,644 people, who had cyclosporiasis from May 13 to July 13 and also visited a Taco Bell to understand the origin of the outbreak.
Michigan and Ohio have seen unusually high numbers of Cyclospora infections this year. The Michigan Department of Health and Human Services is reporting 6,148 cases, with 102 people hospitalized. In Ohio, the Toledo-Lucas County Health Department noted 967 cases of cyclosporiasis in Lucas County and 2,029 total cases in Northwest Ohio.
Most produce remains safe
Health officials are continuing to investigate the sources of the outbreak. Experts said that even if the test result was a false-positive, Taylor Farms products likely contributed to some cyclosporiasis cases this summer.
“The epidemiological results and traceback information is enough to suggest that the product distributed by Taylor Farms is responsible for at least some of the outbreak,” Craig Hedberg, PhD, professor of environmental health sciences in the School of Public Health at the University of Minnesota, told CIDRAP News.
“The recall of the product, food service and retail, suggests that this may have accounted for many of the cases who did not eat at Taco Bell,” he said. “That doesn’t mean that every case of Cyclospora reported this summer is due to products from Taylor Farms, but that they do appear to account for much of the outbreak cases.”
During a media briefing, an FDA official said that traceback information points to Taylor Farms and added that the investigation continues. The official also explained the difficulty of testing for Cyclospora on produce, noting that small amounts of it on fruits and vegetables can cause illness, but tests might not be sensitive enough to detect it.
“Because we cannot grow Cyclospora in the lab, testing of food or environmental samples depends on the sensitivity of the test… and concentration of the organism on the food sample,” Hedberg explained. “They are usually very low. If the contamination is around the level of detection, it may or may not produce a positive signal.”
It takes one to two weeks for the characteristic cyclosporiasis symptoms of severe diarrhea and nausea to begin, which creates a natural delay in investigation. Sometimes, by the time experts test produce, the affected product no longer remains in the food supply.
Hedberg said people should avoid eating recalled lettuce but can still enjoy most fruits and vegetables. “Most of the fresh produce currently in the marketplace can be eaten without undue concern,” Hedberg said. “We should always remember that no fresh produce grown out in the open… is free of risk, and we should all follow general food safety guidelines.”
