The investigation into the source of cyclospora in Texas has been a painstaking process for local health departments and federal officials.
Prebagged salad mix has been blamed as the culprit in Nebraska and Iowa, but a cause has not yet been determined in the North Texas cases.
Finding what's spreading cyclospora is like finding a needle in a haystack.
"Have you ever tried to remember all the foods you've had and what dates you were at various restaurants?" said Dr. Peggy Whittie, Collin County chief epidemiologist.
"Cyclospora was a surprise this year," Whittie said.
Infected patients have to fill out a 16-page questionnaire and write down what they've eaten and where they grocery shopped in the past two weeks. The North Texas cases are then compared with others across the state and the country to see if there are any similarities.
"You've got Dallas, Tarrant, Denton and Collin County," Whittie said. "They most assuredly would be looking at our cases because we're sort of the core here in Texas. There are others in the state, but not as many as we have."
A seven-person team at Food and Drug Administration headquarters in Maryland is dedicated to finding the farm, distribution center or other source of the cyclospora that has sickened nearly 400 people in 15 states. Specialists at 10 national field offices are also collecting thousands of invoices, analyzing shipping documents and tracing the paths of the food eaten by victims.
A Mansfield couple said they were sickened after getting takeout and do not have salad mix at home.
"One minute [you] feel like you got things under control, you feel like you can eat," Danny Wexler said. "You try and eat -- three, four minutes [later], you are into the bathroom."
The Centers for Disease Control and Prevention said it is not clear if produce is to blame for the outbreak in all states, and doctors don't want to be too quick to point the finger.
"Food items have been mentioned, but the main thing everyone keeps coming back to, until they have the right thing, you don't want to pinpoint one item and then it not be the item," Whittie said.
An Iowa food-safety inspector said Wednesday that most, if not all, of the prepackaged salad mix that sickened people in Iowa and Nebraska wasn't grown in either state. At least 80 percent of the vegetables were gown and processed outside both states' jurisdictions, he said.
Officials haven't confirmed the origins of 20 percent and may never know because victims can't always remember what they ate.
Whittie says washing fruits and vegetables, surfaces and your hands is the best thing to do to protect yourself. However, even thorough washing may not eliminate the risk of transmission because cyclospora can be difficult to wash off of all types of produce. Treatment with chlorine or iodine is also unlikely to kill the microscopic parasite.