Cyclospora First Deaths: Expert Explains Why Cases Are So Difficult to Trace and What Infection Preventionists Should Know

The largest documented Cyclospora outbreak in US history has taken a tragic turn. The Michigan Department of Health and Human Services recently confirmed the first 2 deaths associated with the outbreak since it began in May. According to state officials, both individuals had significant underlying health conditions that may have been worsened by cyclosporiasis and dehydration. While Cyclospora infections are rarely fatal, the deaths underscore the serious consequences the parasite can have in vulnerable populations.

The outbreak has now affected 45 states, prompting a joint investigation by the CDC and the US FDA. Contaminated iceberg lettuce imported from Taylor Farms in central Mexico has been identified as 1 source of infections in Michigan and 8 other states, leading to a product recall on July 17. As of July 30, Michigan had reported more than 11,234 cases and 193 hospitalizations, while the CDC had confirmed more than 6,700 cases nationally, with additional investigations ongoing.

Cyclospora cayetanensis spreads through food or water contaminated with human fecal matter. Symptoms typically include prolonged watery diarrhea, nausea, fatigue, weight loss, and abdominal cramping. Although many infections resolve without treatment, antibiotic therapy can shorten the duration of illness, and severe dehydration may require hospitalization. Health officials continue to emphasize proper food handling practices, including thoroughly washing produce and cooking fruits and vegetables to at least 158°F when appropriate.

As public health officials continue to search for sources of contamination, infection prevention and control (IPC) professionals remain critical partners in identifying cases, educating patients, and supporting disease surveillance.

During a recent interview with Infection Control Today^®(ICT^®), Tyler Smith, PhD, statistical epidemiologist and professor at National University, discussed why Cyclospora outbreaks remain among the most difficult foodborne illnesses to investigate, how artificial intelligence may strengthen disease surveillance, and what infection preventionists (IPs) can do to help reduce future outbreaks.

Understanding Statistical Epidemiology

Before discussing Cyclospora specifically, Smith explained that statistical epidemiology is an increasingly important discipline within public health, particularly as health care organizations collect more data than ever before.

"Epidemiology is basically looking at determinants of disease," Smith said. "Epidemiologists are all over the public health spectrum, looking at anything from cancer to outbreaks."

Unlike traditional epidemiology, statistical epidemiology focuses on analyzing enormous population-level datasets generated through electronic health records, surveillance systems, and other health informatics platforms.

"We're able to use those and do predictive modeling for various outcomes, including an outbreak like this," he explained. "We're leveraging advanced predictive analytics to isolate issues, try to find where the sources are coming from, try to find who's infected, and try to mitigate the problems that are out there."

The availability of large-scale health databases has grown substantially over the past 2 decades, particularly following the COVID-19 pandemic, allowing researchers to identify disease trends faster than ever before.

Why Cyclospora Is So Difficult to Trace

Cyclospora outbreaks present unique challenges for public health investigators because contamination often occurs far upstream in the food supply chain, long before patients become ill.

Smith noted that the US has an effective surveillance infrastructure capable of quickly identifying outbreaks. "We have an amazing reporting system in the U.S., and it's quite effective at identifying issues quickly," he said.

However, identifying the exact source remains difficult because of the parasite's unusually long incubation period.

"With a 7-day to 14-day incubation period, that's not always easy to figure out," Smith explained. "People forget what they ate a week ago or 2 weeks ago. It's not that simple to isolate and find out where somebody might have picked it up."

Investigators currently face another complication: evidence suggests there may be more than 1 contamination source.

"Taylor Farms has voluntarily removed some product," Smith noted, "but there appear to be multiple sources or multiple outbreaks. That's why public health practitioners are having difficulties identifying exactly where it's coming from and stopping it."

Even with today's sophisticated databases and surveillance systems, reconstructing an individual's food history over 2 weeks remains a significant epidemiologic challenge.

Putting the Outbreak Into Perspective

Although the number of Cyclospora cases has increased substantially this year, Smith emphasized that outbreaks differ from epidemics and should be viewed within the broader context of foodborne illness.

"There are more than usual," he said. "It's an outbreak. It's not an epidemic."

He compared Cyclospora with other foodborne pathogens that occur much more frequently.

"Escherichia coli (E coli) averages more than 100,000 cases every year," Smith said. "Salmonella averages around a million cases every year."

While Cyclospora has generated considerable public concern, Smith noted that no deaths have been associated with the current outbreak, unlike E coli or Salmonella, which cause fatalities each year.

Nevertheless, the illness can be debilitating.

"There are serious cases, and it scares people because there's so much downtime," he said. "Quite frankly, you lose a lot of weight real quick."

Travel and Global Food Systems Complicate Investigations

Globalization has transformed food production and distribution, creating additional obstacles for outbreak investigations.

"The fact is we're very global in the sense that we travel a lot," Smith said. "So first you've got to figure out: Is this individual getting this here, or did they bring it back from a different country?"

Investigators must also consider where foods originate. Although current evidence points to iceberg lettuce as a possible source, Smith cautioned that the investigation is ongoing.

He stressed that the average consumer has a very low probability of becoming infected.

"The likelihood is very, very small," Smith said. "Very, very small."

Still, he encouraged consumers to understand where both their produce and their water originate.

"Know where your water is coming from," he advised. "Know where your sources of vegetables and fruits are coming from."

AI Shows Promise, but Data Quality Still Matters

Artificial intelligence has become one of the most discussed technologies in health care, and Smith believes it will play an increasingly important role in disease surveillance.

However, he offered an important caveat.

"These tools are only as good as what the data are," Smith said.

Predictive algorithms depend entirely on accurate, timely information.

"If you don't have good data flowing into those algorithms, you don't have good outputs," he explained. "If we have poor data, we're going to have poor results."

While AI can help detect subtle trends that humans might overlook, it cannot compensate for incomplete reporting or inaccurate surveillance information.

Maintaining Public Health Infrastructure

Smith also discussed the importance of sustained investment in public health programs.

Although he believes current surveillance systems remain robust, he warned that public health funding often follows a predictable cycle.

"When public health does really well at stopping an illness...people step back the money and focus it elsewhere," he said.

Unfortunately, reducing resources after outbreaks subside can leave agencies less prepared for the next emerging threat.

"If you don't maintain a good management structure, the issue will come roaring back."

Smith believes COVID-19 demonstrated exactly why continued preparedness matters.

"There have been books and books written about these potential outbreaks and pandemics," he said. "Nobody did much because it wasn't a current issue. But when it became a current issue, then it was all hands-on deck."

Practical Advice for Infection Preventionists

For infection prevention and control professionals, educating patients during the summer produce season, Smith's recommendations were straightforward.

"Wash your fruits and vegetables. Know where the sources are."

Rather than avoiding fresh produce altogether, he encouraged consumers to continue eating fruits and vegetables while practicing safe food handling.

"Don't stop the fruits and vegetables," he said. "Understand where they're coming from, understand how they're sourced, and keep eating them."

He also emphasized basic food safety practices such as using separate cutting boards for meats and produce, thoroughly washing fruits and vegetables, and properly preparing food at home.

"If the basics about cutting boards and scrubbing stuff were done," Smith said, "you would cut down a lot of these issues."

Looking Ahead

As climate change, globalization, and increasingly complex food supply chains continue to influence foodborne disease, Smith believes outbreaks like the current Cyclospora event will persist. However, he expects heightened public awareness following major outbreaks to temporarily improve food safety behaviors.

"There'll be a lot of attention given to it," he said. "Suddenly, a lot of people will start washing their fruits and vegetables better."

Eventually, those behaviors often decline as public concern fades.

For infection preventionists, the larger lesson extends beyond Cyclospora.

"There are points from the field to the plate where we can go wrong, and people can get sick," Smith concluded. "Populations need to understand how to mitigate those issues by proper preparation and understanding where something is coming from. Through this, we'll bypass a lot of the issues, not just Cyclospora."

As statistical epidemiologists continue monitoring population-level data for early warning signs, IPs remain essential in translating those findings into education, surveillance, and practical prevention strategies that protect patients and communities alike.