Nearly 3,000 Sickened in Multi-State Cyclospora Outbreak as Health Officials Race to Identify Source

By Emmanuel Bobby

Health officials across the United States are investigating a widespread outbreak of cyclosporiasis, a foodborne illness caused by the microscopic Cyclospora parasite, after nearly 3,000 people have fallen ill in at least 31 states.

According to the Centers for Disease Control and Prevention (CDC), 86 people have been hospitalized as investigators work to determine what contaminated food item is responsible for the growing number of infections. No deaths have been reported.

The agency said Friday that while outbreaks have been identified in multiple states, investigators have not yet determined whether they all stem from a single contaminated source or represent several unrelated outbreaks occurring simultaneously.

The number of reported illnesses has risen dramatically compared with the same period last year. Of the nearly 3,000 reported cases nationwide, the CDC has confirmed 843 infections that were acquired within the United States while more than 1,500 additional suspected cases remain under investigation.

Michigan Emerges as the Center of the Outbreak

Michigan has experienced the largest surge in infections by far, reporting 1,562 confirmed cases as of Friday. At least 36 patients in the state have required hospitalization.

The outbreak has been concentrated largely in southeastern Michigan near the Ohio border, where neighboring communities have also reported increasing numbers of illnesses.

Ohio has recorded at least 177 confirmed cases and 28 hospitalizations, although those figures are expected to rise. The Toledo-Lucas County Health Department alone reported more than 300 cases during the past week.

New York has documented 394 cases, while Illinois has reported 141 infections. Additional cases have been identified in Colorado, North Carolina, Texas, Wisconsin, and numerous other states.

Based on state health department reports, nearly 3,000 confirmed or probable cases have now been identified nationwide, already surpassing the total seen during much of last year’s outbreak season.

Health Officials Call Surge ‘Highly Unusual’

Dr. Natasha Bagdasarian, Michigan’s chief medical executive, described the scale of the outbreak as extraordinary.

Michigan typically records only 40 to 50 cases of cyclosporiasis during an entire year, making this summer’s surge unlike anything public health officials have previously encountered.

Laboratories throughout the state are now performing genetic sequencing on Cyclospora samples to determine whether patients were infected by the same strain of the parasite.

Scientists hope comparing the genetic fingerprints of the organisms will help investigators determine whether infections originated from a common contaminated food source.

“If isolates are closely related, meaning that there was likely a common source, then we can potentially go back and identify where that contamination occurred,” Bagdasarian explained.

Fresh Produce Remains the Leading Suspect

Although investigators have not yet identified the contaminated product responsible for the current outbreak, history suggests fresh fruits, vegetables, or herbs are the most likely culprits.

Cyclospora parasites commonly attach themselves to produce such as lettuce, cilantro, basil, raspberries, and salad greens. Because the parasite clings tightly to the surface of produce, simply rinsing fruits and vegetables often cannot remove all contamination.

Previous outbreaks have been linked to imported raspberries, packaged salad mixes, fresh cilantro, basil, and leafy greens.

Federal officials stress that no specific food product has yet been identified in the current outbreak, and no recalls have been issued.

The U.S. Food and Drug Administration said it is actively working with state health agencies to trace the source of the contamination.

Why Investigating Cyclospora Is So Difficult

Tracking Cyclospora outbreaks presents unique challenges for epidemiologists.

Unlike many foodborne illnesses that cause symptoms within a day or two, Cyclospora infections often take about one week—or even longer—to develop after contaminated food is consumed.

By the time patients become ill, many struggle to remember everything they ate during the previous several weeks.

Adding to the difficulty, contaminated ingredients are frequently hidden within prepared foods.

Fresh cilantro mixed into salsa, basil blended into sauces, or lettuce included in restaurant salads may not stand out in a person’s memory days later.

Dianna Blau, acting chief of the CDC’s Parasitic Disease Branch, said only a small percentage of Cyclospora cases are ultimately traced back to one specific food item during a typical year.

What Is Cyclosporiasis?

Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis. Infection occurs after people consume food or, less commonly, water contaminated with the parasite.

Unlike viruses such as norovirus, Cyclospora cannot spread directly from one person to another.

Instead, the parasite must spend several days or even weeks maturing in the environment before it becomes capable of infecting another individual.

Because of this life cycle, outbreaks almost always originate from contaminated food rather than person-to-person transmission.

Symptoms Can Be Severe

Symptoms usually begin about one week after consuming contaminated food.

Many patients first experience fatigue, body aches, and flu-like symptoms before developing the illness’s hallmark symptom—profuse, watery diarrhea that can become severe and difficult to control.

Other common symptoms include:

• Persistent watery diarrhea
• Stomach cramps
• Excessive gas and bloating
• Nausea
• Loss of appetite
• Fatigue
• Weight loss
• Occasional low-grade fever

Without treatment, symptoms can continue for several weeks and may recur even after temporarily improving.

Doctors typically prescribe the antibiotic trimethoprim-sulfamethoxazole, commonly known by the brand name Bactrim, which is considered the standard treatment.

Patients are also encouraged to drink plenty of fluids because dehydration from prolonged diarrhea is one of the leading reasons people require hospitalization.

Health experts estimate roughly one in every ten infected patients is hospitalized, with young children, older adults, and people with weakened immune systems facing the highest risk of serious illness.

Concerns About Disease Surveillance

The outbreak has also renewed discussion about foodborne disease monitoring in the United States.

Last year, the CDC made Cyclospora surveillance optional under changes to its Foodborne Diseases Active Surveillance Network, prompting concerns among some food safety experts that outbreaks could become harder to detect.

Donald Schaffner, a professor of food microbiology and chair of the Department of Food Science at Rutgers University, questioned whether earlier detection might have been possible under previous surveillance practices.

“We need to be doing more to track these,” Schaffner said.

CDC officials maintain that the agency’s handling of Cyclospora cases has not significantly changed and say investigators continue working closely with state and local health departments.

Public health workers are interviewing patients, reviewing grocery receipts, identifying common food purchases, and comparing laboratory samples in an effort to determine whether infections across different states are connected.

How to Reduce Your Risk

Although no specific food has been identified as the source of the current outbreak, health officials recommend continuing to eat fresh fruits and vegetables because of their well-established health benefits.

Experts emphasize that consumers should not stop eating produce altogether while investigators search for the source.

Cooking remains the most reliable method for killing the Cyclospora parasite.

While washing produce under running water can reduce contamination, it cannot completely eliminate the risk because the parasite adheres tightly to surfaces.

Food safety specialists advise against washing produce with dish soap, which can leave harmful residues. Instead, fruits and vegetables should be rubbed or gently scrubbed under running water.

Michigan health officials recommend several additional precautions:

• Purchase whole heads of lettuce instead of pre-packaged salad mixes when possible.
• Remove and discard the outer lettuce leaves before washing.
• Separate cilantro and basil leaves thoroughly while rinsing.
• Trim the roots and remove outer layers of green onions before washing.
• Cook berries when practical, such as when making pies, jams, or sauces.

Although raspberries have been associated with previous Cyclospora outbreaks, investigators have found no evidence linking them to the current surge in illnesses.

Food safety experts continue to encourage consumers to maintain healthy eating habits while practicing careful food handling as investigators work to identify the source of one of the nation’s largest Cyclospora outbreaks in recent years.