Researchers work to develop faster, more accurate virus detection for produce

Researchers in Spain are working to develop faster, more accurate methods for detecting viruses like human norovirus and hepatitis A in fresh produce.

The project, led by Dr. Susana Guix from the University of Barcelona, aims to improve food safety and reduce false positives. It focuses on leafy greens and berries, which are often associated with contamination risks.

“It’s very difficult to grow viruses in the laboratory as we do bacteria, so we have to rely on molecular methods to test,” Guix said. “If viruses are on produce, they’re usually in very low numbers and at very low concentrations, so we need to have very good extraction procedures.”

Aiming for better accuracy and efficiency
Currently, virus testing in produce involves time consuming sampling and concentration processes, which can result in inaccurate results. Guix’s research, conducted in collaboration with Dr. Gloria Sánchez Moragas of IATA-CSIC in Valencia, Spain, seeks to streamline these procedures. Sánchez’s expertise in molecular detection complements Guix’s focus on cell culture techniques.

The team developed two alternative virus extraction and concentration protocols, testing them against the industry standard protocols from the U.S. Food and Drug Administration (FDA) and the International Organization for Standardization (ISO). Using leafy greens and berries spiked with known quantities of human norovirus or hepatitis A virus, they evaluated recovery rates.

The results showed that a commercial extraction method recovered significantly more viruses from leafy greens, raspberries, and blueberries than the FDA or ISO protocols. For strawberries, the commercial method performed comparably to the FDA standard. The researchers also combined their extraction method with a modified RTqPCR assay, which quantifies RNA from viruses. This combination reduced false positives by identifying non-viable hepatitis A viruses than existing protocols.

“So far, it’s given us better results for hepatitis A virus and norovirus on six different types of food, and the results are consistent,” Guix said.

Real-world applications
In the second year of the study, the researchers plan to use their improved methods to assess virus die-off under simulated post-harvest conditions. They will also evaluate the efficacy of three commonly used disinfectants for leafy greens: chlorine, chlorine dioxide, and peracetic acid.

The study is expected to benefit the produce industry by providing faster and more accurate biological analyses, enabling better assessments of contamination risks. Additionally, the research aims to fill critical knowledge gaps about the persistence of infectious viruses on produce during storage and after disinfection.

Although the research is based in Spain, Guix believes its impact will be global. “I think the two labs are complementary,” she said, noting that both teams conducted concurrent assays to ensure robust results.

The findings will be presented at the 2025 Center for Produce Safety Research Symposium in La Jolla, California, on June 17-18. The Center for Produce Safety, a U.S.-based nonprofit focused on produce safety research, is funding the project.

For more information about the study and the Center for Produce Safety, visit their website.

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