Courtesy NBC News

As the number of people sickened by a parasite that causes intestinal illness rose to more than 275, Dr. Nancy Snyderman offered this simple yet vitally important advice on TODAY Thursday: Wash your hands and wash your produce.

The Centers for Disease Control and Prevention is investigating an outbreak of cyclospora infection, which has affected people in at least nine states from New Jersey to Texas. Ten people reportedly have been hospitalized because of the parasite, and most cases have occurred since mid-June through early July.

"The cyclospora parasite can be nasty, causing flu-like symptoms that can last up to a month, and doctors say this outbreak is spreading," said Snyderman, NBC's chief medical editor.

Although the source of the outbreak has not been identified and it is not known whether the cases are connected, Snyderman said the infection is most commonly contracted by eating tainted fruits and vegetables. With so much produce being imported across states lines and from other countries, she urged consumers to check the origin of their produce and clean the fruits and veggies thoroughly.

"You're not going to get this, most likely, from your local farmer's market," she told TODAY's Matt Lauer. "A lot of times, these things come from other countries, so read those product labels well. Even when you get those pre-washed greens, don't believe it. Wash them again."

Lauer asked if an ill person could spread it to another, but Snyderman said hand-washing should take care of that potential problem. "Once you wash your hands and rid yourself of it, it's not a problem," she told him.

The symptoms range from loss of appetite and fatigue to nausea and diarrhea, Snyderman said. There is "not a high death rate but people who are sick are really sick," she said.

Only a specific test can confirm the diagnosis, Snyderman said, noting that the symptoms could be the sign of other illnesses. There is one antibiotic that is effective against the parasite, she said.

Dr. Shawn Mitchell, of Premier Urgent Care in Colleyville, Texas, told TODAY: "People need to be concerned but there is no need to panic widespread."

With news of the outbreak, some people are wondering whether the parasite has struck their family.

In Keller, Texas, Paul Littlejohn believes grapes may have caused his illness, and he went to his doctor when his symptoms persisted. "He said, ‘Yeah, there is an intestinal bug going around, and so you probably have that,'" he said.

As one Connecticut mother shopped for produce, she too wondered whether the parasite was to blame for her daughter's recent illness. "My daughter was at pediatrician yesterday for severe stomach cramps and nausea," she told TODAY.

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