Cyclospora Outbreak in the United States: Why Rapid Molecular Testing Matters for Gastrointestinal Pathogens

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Cyclospora cases are increasing across the United States

Health authorities are investigating a growing outbreak of Cyclospora cayetanensis, the parasite responsible for cyclosporiasis. Cases have been reported across numerous states, with investigators continuing to determine the food source responsible for the outbreak. Historically, Cyclospora outbreaks have been linked to fresh produce such as leafy greens, herbs, berries, and other foods consumed raw. Because fresh produce is often distributed widely before contamination is recognized, a single contaminated food item can result in cases reported across multiple states, making laboratory confirmation and epidemiologic investigations important for identifying outbreak sources.

Cyclospora infection typically causes:

• Watery diarrhea
• Loss of appetite
• Abdominal cramping
• Bloating
• Nausea
• Fatigue
• Weight loss

Unlike many foodborne illnesses, symptoms often begin about one week after exposure and may persist for weeks if untreated. Because the symptoms resemble many other gastrointestinal infections, laboratory testing is important for identifying the causative pathogen.

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Why Cyclosporiasis can be difficult to diagnose

Cyclospora is only one of many organisms capable of causing infectious gastroenteritis.

Individuals with acute diarrhea may instead be infected with bacterial pathogens such as Salmonella, Campylobacter, or Shigella, viral pathogens such as norovirus or rotavirus, or other parasites including Giardia and Cryptosporidium. Symptoms frequently overlap, making it difficult to determine the underlying cause based on symptoms alone.

This is why comprehensive laboratory testing has become increasingly valuable.

Did you know?

Symptoms alone cannot distinguish Cyclospora infection from bacterial, viral, or other parasitic causes of gastroenteritis, making laboratory testing important for diagnosis.

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How is Cyclospora detected?

Because diarrheal illnesses often have similar presentations, molecular testing that simultaneously evaluates multiple bacterial, viral, and parasitic organisms can provide a more comprehensive approach than testing for individual pathogens alone.

Testing approaches may include microscopy with specialized staining techniques, molecular PCR assays, or multiplex gastrointestinal pathogen panels that simultaneously evaluate bacterial, viral, and parasitic organisms. Not all stool tests include Cyclospora, making appropriate test selection important when infection is suspected (CDC).

Diagnostic Method	Detects Cyclospora	Detects Multiple Pathogens	Typical Workflow
Stool culture	No	Limited	Multiple assays
Microscopy	Yes	No	Manual examination
Multiplex PCR	Yes	Yes	Single specimen, multiple targets

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The advantages of molecular testing for gastrointestinal pathogens

Traditional detection methods such as culture or microscopy, remain important tools but can require multiple workflows, longer turnaround times, and additional confirmatory testing for certain organisms.

Real-time PCR-based molecular testing offers several advantages:

• Rapid time to results; results in hours vs days for traditional methods
• High analytical sensitivity and specificity
  • Due to this high analytical sensitivity, you don’t need to culture samples to test by qPCR
• Simultaneous detection of multiple pathogens from a single stool specimen
• Reduced need for sequential or reflex testing
• Automated data interpretation to minimize manual analysis

Because one sample may contain several potential pathogens—or because researchers may not know which pathogen is responsible—multiplex molecular testing enables laboratories to evaluate a broad range of bacterial, viral, and parasitic targets in one workflow. Molecular testing can also reduce the need for multiple sequential tests when the causative pathogen is unknown.

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Why comprehensive GI panels matter during outbreaks

Individuals evaluated during suspected foodborne outbreaks may have infections caused by different bacterial, viral, or parasitic pathogens, and coinfections can also occur. Comprehensive testing helps laboratories differentiate among potential causes using a single specimen.

Individuals presenting with diarrhea may have infections caused by:

• Bacteria
• Viruses
• Parasites
• Coinfections involving multiple organisms

Testing for a broad range of gastrointestinal pathogens helps laboratories identify the responsible organism more efficiently while reducing the need for multiple individual assays.

During outbreaks involving organisms such as Cyclospora, this broader approach can support more complete laboratory investigations and improve workflow efficiency.

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The role of laboratory surveillance

Laboratory surveillance plays an important role in identifying Cyclospora cayetanensis infections and supporting public health investigations. Because cyclosporiasis is a nationally notifiable disease in the United States, confirmed cases are reported to public health authorities, allowing the CDC, in collaboration with state and federal partners, to monitor cases year-round and identify outbreaks linked to a common food source.

Since symptoms often develop approximately one week after exposure and are not specific to Cyclospora, timely laboratory testing is important for detecting cases and supporting epidemiologic investigations. Molecular testing that includes Cyclospora cayetanensis alongside other gastrointestinal pathogens can support surveillance and research by enabling efficient detection from a single specimen (CDC).

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How Thermo Fisher Scientific supports GI pathogen research and surveillance

Thermo Fisher Scientific has developed an assay for the detection of Cyclospora cayetanensis, available in several formats in the TrueMark Enteric research solutions gastrointestinal pathogen portfolio.

Whether laboratories choose:

• TrueMark Enteric Select Panels
• TrueMark Enteric Expanded OpenArray Panels

The Cyclospora assay is consistent across the GI research product family, allowing laboratories to select the workflow that best matches their throughput and research requirements while maintaining coverage for this important parasitic target.

The portfolio also enables simultaneous identification of numerous additional bacterial, viral, and parasitic pathogens commonly associated with infectious gastroenteritis, helping provide a more complete picture from a single specimen. Comprehensive molecular workflows may help laboratories support outbreak investigations, surveillance programs, seasonal monitoring, and gastrointestinal pathogen research.

Note: TrueMark Enteric products are For Research Use Only. Not for use in diagnostic procedures.

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Choosing the right workflow

Thermo Fisher Scientific offers multiple molecular testing formats designed to accommodate different laboratory needs.

TrueMark Enteric Select Panels

• Single-tube multiplex real-time PCR
• Targeted bacterial, viral, or parasitic panels
• Flexible testing based on laboratory needs
• Compatible with QuantStudio real-time PCR systems

TrueMark Enteric Expanded Panels

• Broad bacterial, viral, and parasitic coverage
• Available in OpenArray formats
• Higher-throughput testing options
• Suitable for laboratories seeking extensive pathogen coverage

Across the portfolio, laboratories can access analytically sensitive molecular identification with scalable workflows designed for gastrointestinal pathogen research.

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Looking ahead

As public health agencies continue investigating the current Cyclospora outbreak, laboratories remain essential partners in identifying and investigating gastrointestinal pathogens and supporting outbreak investigations.

Because diarrheal illnesses often present similarly, comprehensive molecular testing that simultaneously evaluates bacterial, viral, and parasitic organisms can help provide a more complete picture than testing for individual pathogens alone.

Including Cyclospora cayetanensis within broader gastrointestinal pathogen panels helps laboratories support seasonal surveillance, foodborne outbreak investigations, and enteric pathogen research.

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Frequently Asked Questions

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Reference

https://www.cdc.gov/cyclosporiasis/outbreaks/07-26/index.html

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