New York City health officials are investigating a continued rise in cases of cyclosporiasis, a parasitic illness typically spread through contaminated food or water. 

As of July 10, there have been 403 cases of cyclosporiasis this year, according to the Department of Health. Health officials say they are working to identify a common source of the infections. 

Cyclosporiasis is caused by the parasite Cyclospora cayetanensis. People can become infected by eating food or drinking water contaminated with the parasite, according to the CDC and the city’s DOH. 

The DOH said outbreaks have been linked to imported fresh produce, including raspberries and cilantro. Unlike many other gastrointestinal illnesses, it does not spread directly from person to person.  

Symptoms typically develop about one week after exposure and include watery diarrhea, frequent bowel movements, stomach cramps, bloating, nausea, vomiting, fatigue, muscle aches, weight loss and a low-grade fever, according to the DOH. 

"What we get is your typical stomach bug symptoms, which include watery often copious diarrhea,” said Dr. Erin Muckey, chief medical officer and vice president at Northwell Greenwich Village Hospital. “You're also seeing stomach cramps, bloating, sometimes a low-grade fever and nausea.” 

"If not treated, it can come and go for months. So, the classic piece about cyclosporiasis, it's different from your classic stomach flu," Muckey said. "Rather than your flu, which is going to hit really hard and then resolve fairly quickly, this can really linger." 

Muckey says washing fruits and vegetables is a good start when it comes to protecting yourself from cyclosporiasis. 

"What is best practice is to cook your produce — so that is above 150 degrees — [that] does kill the parasite," she said. 

Muckey recommends that when eating salads that can’t be cooked, swap the bags of lettuce for heads of lettuce, and remove the outer two layers of leaves before thoroughly washing the rest. 

She said says the infection responds well to antibiotics but children, adults over 50, those with weakened immune systems or those who are pregnant should be especially vigilant for dehydration that can result from the illness. 

Muckey recommends asking a health care provider to test for cyclosporiasis if gastrointestinal symptoms improve and then return. 

The city's investigation comes as infections continue to rise nationwide. More than 30 states have reported cyclosporiasis cases this year, and federal health officials said Tuesday that infections in at least four states — Michigan, Ohio, Kentucky and West Virginia — appear to be linked. 

Michigan, which has reported more than 3,300 cases, says early findings point to lettuce or salad greens as a possible source.