Aug. 6, 2013 -- Megan Provost ate a salad at Olive Garden six days before the onset of what she called the worst stomach bug of her life.
"I felt like somebody socked me in the stomach," Provost, a 29-year-old banker, said. "I wouldn't wish this on my worst enemy."
After learning about the multi-state cyclospora outbreak tied to Olive Garden in Nebraska and Iowa, she said she's "100 percent sure" that she had the illness caused by a one-celled parasite and spread through contaminated food. Cyclospora has sickened 425 people in 16 states so far.
But Provost is in Kansas, where investigators have reported only one case of the stomach bug that originated within the state, and officials don't believe it's associated with the outbreak. Provost is still awaiting test results to confirm her cyclospora infection with the Centers for Disease Control and Prevention, so she is not included in the state's three reported cases, two of which originated in Iowa and Nebraska.
"It is possible that the ... case in Kansas is a sporadic case that was detected because of increased awareness of cyclospora among the public and health care providers," said Kansas state epidemiologist D. Charles Hunt. "But it is not possible to determine a potential source with just one case."
The Food and Drug Administration announced Friday that Taylor Farms, which supplies pre-packaged salad to Darden restaurants such as Olive Garden and Red Lobster, was responsible for the outbreak of cyclospora, but only in Nebraska and Iowa.
"It is not yet clear whether the cases reported from other states are all part of the same outbreak,"said FDA spokeswoman Theresa Eisenman. "The investigation of increased cases of cyclosporiasis in other states continues."
Food safety experts say cyclospora is too rare for the cases to be unrelated, but many questions remain.
"Cyclospora is rare -- especially in the US -- so the chances of most, not all, not being related to the same product and/or manufacturer is very, very slight," foodborne illness lawyer Bill Marler said in an email.
Although Nebraska and Iowa are home to 232 of the 425 cases, health officials haven't determined how the remaining 193 cyclospora victims picked up the parasite.
In Texas, where 127 people have confirmed cyclospora cases, Darden restaurants don't get their salads from Taylor Farms, Darden spokesman Rich Jeffers told the Orlando Sentinel. When ABCNews.com asked the farm who else it supplied in Texas, it dodged the question and referred further questions to Darden.
Health officials in Texas are interviewing patients, but they haven't linked their illnesses to salad products from Taylor Farms, said Texas Department of State Health Services spokeswoman Christine Mann.
"The Department of State Health Services is interviewing cases -- and so are local health departments -- to try to figure out a common source," she said. "At this point, we haven't determined any links."
In Florida, officials haven't linked their 25 cyclospora cases to the salad mix, but they can't rule it out either, said state health department spokeswoman Erica Chicola.
"Whether we can say something more definite will depend on whether the FDA can do a 'trace forward' that proves the product was sent to Florida, and if there is a link between product distribution and the shopping patterns of the Florida cases," Chicola said.
The investigation is difficult because of how salads are mixed together from different fields and are sold under different brand names, said Christopher Waldrop, who directs the Food Policy Institute at the Consumer Federation of America.
"The hope is that the spikes are all connected and they're able to determine conclusively that the ones in Texas and other states are part of the larger outbreak," Waldrop said. "But it sounds like they just don't have the proof yet."
Marler said cyclospora patients in states not yet tied to Taylor farms may have eaten food from the same growing area or processing facility but whose products are sold under different brand names. Or it could be a different cross-contaminated product altogether.
Lawyer Tony Coveny of law firm Simon and Luke, who focuses on food poisoning and represents Provost and about a dozen other cyclospora victims, said he's not surprised the FDA and the Centers for Disease Control and Prevention need more time to confirm the source of the outbreak. If they announce the wrong name, it will cost that company millions of dollars and could damage the FDA's relationship with members of the food industry for other future investigations.
"The nice thing about salads being linked to a particular batch is that they have a short shelf life," he said, adding that it's fortunate that the product at the center of the outbreak isn't a canned good with a long shelf life. "It's less likely to have a huge public impact by failing to recall the lettuce. It's only on the shelf a week or two anyway."
Although Provost is 15 pounds lighter than she was before she became infected with cyclospora at the end of June, she said she's doing better after a trip to the emergency room and a round of antibiotics. Although she gets a sense of relief having an idea of where her illness came from, she said she wishes she'd known earlier.
"It makes me upset that it wasn't disclosed sooner," she said. "That [Olive Garden is] where it came from and I've been wondering."