(USA Today)-- Food safety experts are beginning to grumble that an investigation into the latest food-borne illness is taking too long to find the exact source of the outbreak. Two states, Iowa and Nebraska, have reported they believe the outbreak is linked to prepackaged, bagged salad mix, but others aren't so sure.
The number of victims in the national outbreak of the food-linked diarrheal disease cyclospora rose to 397, with illnesses reported in 16 states, the Centers for Disease Control and Prevention reported late Wednesday.
The CDC says it is working to determine whether the possible link to bagged salad mix applies to cases in other states as well.
The Food and Drug Administration "can't speak to an ongoing investigation," said FDA spokeswoman Theresa Eisenman.
"With 390-some people ill, you'd think it would be fairly easy to triangulate the trace back" to the food causing the illnesses, said Dave Gombas, senior vice president for food safety with United Fresh Produce Association, a produce trade group in Washington, D.C. "So the fact that FDA and CDC aren't going along with Iowa and Nebraska gives me pause."
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Cyclospora is an intestinal illnesses caused by the microscopic parasite Cyclospora cayetanensis. It is transmitted when feces enter the food or water supply and are consumed. The disease causes watery and sometimes explosive diarrhea and is treated with antibiotics. Symptoms can include fatigue, anorexia, bloating, stomach cramps, vomiting, muscle aches and a low fever.
At least 22 people in five states have been hospitalized in the outbreak.
Iowa's public health system first caught the outbreak on June 25 when Michael Last, a parasitologist at the State Hygienic Laboratory at the University of Iowa in Coralville, recognized the parasite in a stool sample sent in by a physician for testing.
He is "a good, good, good microbiologist," said Patricia Quinlisk, Iowa's state epidemiologist.
The parasite is rarely seen in the United States. "We haven't had a major outbreak from cyclospora in almost a decade," said Caroline Smith DeWaal with the Center for Science in the Public Interest in Washington, D.C. Her database shows the most recent large outbreak was in Florida in 2005, where 592 people were sickened with contaminated basil. The nation's largest-known cyclospora outbreak was in 1996 when raspberries from Guatemala sickened 1,465 in multiple states, she said.
Using Twitter, Facebook and other media, Iowa officials made sure health workers across the state were looking for similar illnesses. Very quickly more cases came in, including from Nebraska next door. Most of the patients had gotten sick in mid-June.
"At the peak of this outbreak we were seeing anywhere from seven to 12 new cases a day," said Mary DeMartino, who runs Iowa's Disease Control Division of the State Hygienic Laboratory.
Iowa health workers established that about 80% of the people who'd gotten sick had eaten the same brand of prepackaged salad mix containing iceberg and romaine lettuce, carrots and red cabbage. Packaged lettuce has a short shelf life, so by the time investigators began interviewing people "the bags were long gone," Quinlisk said. That means there wasn't anything for them to test to see which of the mix's four ingredients was responsible for the illnesses.
The last person Iowa tested got sick on June 28. State officials believe the tainted lot of salad mix is gone from store shelves and the outbreak is waning there. What's going on in other states is difficult to say because "their epidemiology looks a little different," Quinlisk said.
It wouldn't surprise her at all if there were more than one outbreak going on, Quinlisk said. "When we look at the data from other states, the people who are getting ill are not necessarily the same as we saw; they're not getting sick at the same time." Bagged salad may not explain all the illnesses in the nation.
Some of the food safety world feels the investigation has not moved as quickly as it should have. "This thing should have been solved a month ago," said Michael Osterholm, Minnesota's former state epidemiologist who now directs the Center for Infectious Disease Research and Policy at the University of Minnesota.
The fact that patrons of a large number of restaurants became ill, including several national chains, "should have helped them," he said. "They were national chain restaurants all owned by one company, which in turn got its ingredients from a single source."
Finding the culprit isn't easy and takes time, Quinlisk said. "Most people's idea of an outbreak is everybody went to the same grocery store and bought the same item. It's not like that. It wasn't one brand name, it was a salad mixture that came into Iowa in a variety of ways in different packaging."
Another issue is that Iowa, like at least 30 other states, has laws on the books protecting agricultural producers. These laws encourage states not to make public information about possible contamination of food that might harm sales unless there is an ongoing outbreak that puts people at risk.
"They don't say 'Thou shall not tell who the business is,'" said Bill Marler, a lawyer in Seattle who has been involved in food-borne illness outbreaks for decades. Instead it's a discretionary decision that has led to a "culture of non-disclosure" that he and others believe is hampering the investigation.
"This ain't done yet. I think the investigation has a long way to go," Gombas said.