US health authorities are struggling to identify the source of a foodborne illness that causes severe diarrhea and dehydration. At least 145 people across 17 states have tested positive for the cyclospora cayetanensis parasite.

The Centers for Disease Control and Prevention (CDC) has acknowledged that there are likely far more cases that are going undiagnosed.

Twenty people have been hospitalized due to the outbreak since early May, although no fatalities have been reported.

New York has emerged as a major hotspot, with between 31 and 80 people contracting the parasite.

Cases of cyclosporiasis have also been identified in Alaska, Colorado, Connecticut, Florida, Georgia, Illinois, Louisiana, Massachusetts, North Carolina, Ohio, Pennsylvania, Tennessee, Texas, Virginia and Wisconsin.

The illness typically causes explosive, watery diarrhea, along with a range of other gastrointestinal symptoms, including bloating, gas, stomach cramps, nausea, and vomiting. Some people also report fatigue and fever, while others develop no symptoms at all.

Cyclosporiasis is usually contracted by consuming food or water contaminated with feces, with symptoms typically appearing about a week after exposure, according to the CDC.

While the illness can be treated with antibiotics, it is not detected by most routine laboratory tests, resulting in a considerable number of undiagnosed cases. If left untreated, the infection can last for over a month, with recurring bouts of diarrhea being its most characteristic feature.

The microscopic parasite is endemic in tropical and subtropical countries, including Guatemala, Peru, and Nepal. There is no evidence that it is capable of human-to-human transmission.

Since most of the individuals diagnosed with cyclosporiasis during the course of the ongoing outbreak had not recently traveled outside the US, health officials suspect that the source is domestically distributed produce.

“Local, state, and federal (CDC, FDA) public health authorities are investigating several clusters of cases in more than one state. Investigations to identify potential sources are ongoing,” according to officials.

Previous cyclosporiasis outbreaks in the US have been linked to cilantro, raspberries, sweet peas, lettuce, and basil imported from Mexico.

The CDC recommends washing leafy greens with cold running water to minimize the risk of exposure.