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Public health officials are still investigating how an outbreak of cyclospora, a parasite spread through human feces, ended up in the public food supply.
Thousands of people across the country have gotten sick from the parasite, which causes frequent diarrhea.
In an ongoing investigation, U.S. Centers for Disease Control and Prevention and the Food and Drug Administration officials have linked part of the outbreak to Taylor Farms iceberg lettuce sourced from central Mexico. The product is sold at retail stores and restaurants, but the company issued a voluntary recall earlier this month.
Typically, cyclospora reaches the food supply through contaminated water. Byron Chaves, food safety specialist at Rutgers University said the water can end up in fields when it’s used to irrigate crops or mixed to dilute pesticides.
“So in this case that is the most likely scenario, right? It's through irrigation water or some kind of contact water,” Chaves said.
This is not the first time cyclospora-caused illness has been reported in the U.S., but it is the largest number of cases the country has seen. Kristen Gibson, director of the University of Arkansas Center for Food Safety, said officials already know the human is the host, so they just need to determine how it ended up in food.
“So that food part, like what is the food exactly, is difficult no matter what type of pathogen you're dealing with that has contaminated the food supply.” Gibson said.
‘A series of unfortunate public health events’
CDC officials are investigating an outbreak in nine states and other clusters of cyclosporiasis. But the illness has been reported in 41 states including in most of the central U.S.
Although federal health authorities have confirmed about 4,100 cases since May 1, about 7,400 additional infections have been reported through state and local health departments, according to the CDC. Federal health officials say they require further analysis.
Some states are listing more cases than that. Michigan alone reports more than 9,000 cases as of July 23.
Wade Syers, food safety specialist with the Michigan State University Extension, said the outbreak’s size is unique. At this stage in the investigation, he said a sure cause for the high number of cases is unclear.
“So I don't want to come out and give one exact reason, but what this, kind of, could point to is a mass contamination event, or it could just be that the conditions were right for this parasite at this time of year,” Syers said.
For cyclospora, he said there is a big variation in how long it takes for people to show symptoms after being exposed. Generally, Syers said it could be anywhere from two days to a couple of weeks.
There are also challenges in tracking the parasite, Chaves said. U.S. detection systems for more common microbes like E. coli or Listeria are quick, reliable and cost effective, he said. But for cyclospora, which is only seen occasionally in the U.S., he said the detection is slower and many testing labs can’t test for it.
Traceability is also hard because lettuce in a bagged salad from the grocery store can come from multiple farms and be mixed up in a processing facility, he said. There’s also lots of people who will contract the parasite but have no symptoms, and the outbreak is widespread.
“It's a series of unfortunate public health events. This is how I've been describing this, because there's just way too many factors,” Chaves said.
As cyclosporiasis cases are reported, Gibson, at the University of Arkansas Center for Food Safety, recommends keeping track of public health notices and product recalls. But she said it's important to remember that we eat produce all the time and do not get sick.
“These types of failures happen,” Gibson said. “And the best thing we can do is try to gather as much information as we possibly can, to be sure that we either put new measures or preventive controls in place so it doesn't happen again.”
Syers, the food safety specialist at Michigan State, said that cooking vegetables thoroughly to 158 degrees kills the microbe.
Syers also recommends following general food hygiene practices, such as washing your hands before, during and after preparing food, or rinsing produce – even though washing produce alone is not an effective way to kill the parasite.
Not all fresh fruits and vegetables have been contaminated, and he stresses produce is still an important part of people's diet.
“We don't have to go all out on an avoidance,” Syers said. “We don't have to be afraid of produce.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
