"It can be pretty miserable, because it can give diarrhea that can last for days," Parise said.
The first reported cases occurred in Iowa, which has been hardest hit with 146 people falling ill so far. The first cases came in late June, with more infections reported through July.
Other states reporting large numbers of infections are Nebraska, with 81 cases, and Texas, with 113 cases.
It takes about a week for people who are infected to become sick.
Marshall said there may be more cases of cyclospora infection out there than people realize. It is possible, "that most occurrences go unreported as many people wouldn't recognize the symptoms as any different than a common stomach bug," he explained.
Dr. Thomas Frieden, CDC director, urged people who have suffered from diarrhea for longer than a couple of days to be tested for cyclospora.
"If not treated, symptoms can last from a few days to a month or longer, go away and then return later," Marshall said. "Cyclospora can be treated with an antibiotic combination of trimethoprim-sulfamethoxazole [Bactrim]."
The best option, however, is to avoid the bug altogether.
"The safest way to protect oneself and one's family is to always rinse fresh produce under water, and even put vegetables in a cold water bath ahead of time to properly clean them," Marshall advised.
One expert stressed that the wash-your-produce rule includes pre-packaged salads.
"Wash all your fruits and salads before ingesting," said Dr. Salvatore Pardo, vice chairman of the emergency department at Long Island Jewish Medical Center in New Hyde Park, NY. "My hunch is the public does not do this to "prepackaged" salad, which is normally purchased for convenience and dumped into the bowl since it tends to be free from particles -- dirt, sand, critters -- one would normally find in locally picked ingredients."
Earlier outbreaks of cyclospora have been traced back to fruits and vegetables imported from tropical regions like Latin America and Southeast Asia, where the parasite is common, Parise said.