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  5. Microbiological Surveillance Sampling: FY 19-23 Frozen Berries (Strawberries, Raspberries and Blackberries)
  1. Sampling to Protect the Food Supply

Microbiological Surveillance Sampling: FY 19-23 Frozen Berries (Strawberries, Raspberries and Blackberries)

Microbiological Surveillance Sampling Main page

Seeking to better understand the occurrence of hepatitis A virus (HAV) and norovirus in frozen strawberries, raspberries and blackberries, the U.S. Food and Drug Administration collected and tested more than 1,500 samples of the three commodities from November 2018 to September 2023 as part of its prevention-based work and mission to keep contaminated food from reaching consumers.

Fresh and frozen berries have been linked to outbreaks of HAV and norovirus infections in several countries, including in the United States. The outbreaks prompted the FDA to conduct this assignment to gain insights into the risks of HAV and norovirus associated with the three commodities.

Assignment Overview

In all, the FDA collected and tested 1,558 samples of the three frozen commodities (585 strawberries, 528 raspberries, and 445 blackberries) for this assignment. The total is less than the number of samples that the FDA set out to collect and test because the agency encountered circumstances that necessitated adjustments to the collection scheme, including to the collection target, as explained in the Sample Collection section of this report.

As to the design of the assignment, the FDA sought to estimate the HAV and norovirus contamination rates in both domestic and import samples for each type of berry, and secondarily to compare them by origin (i.e., domestic versus import). The agency collected samples in finished packaging and from bulk containers. The agency did not collect berry pulp or frozen berries with added ingredients.

Ten months into the assignment, the agency ceased its collection of samples at retail in favor of sampling at earlier stages of the distribution chain so that, per industry common practice,[1] greater volumes of product impacted by testing would be held prior to entering commerce or not enter commerce in the event of a pathogen detection. In making this update, the agency’s intent was to better protect consumers while minimizing market disruption. 

Additionally, after engaging in dialogue with external interest holders, the FDA in the first year of the assignment strengthened its testing protocol by adding amplification and subsequent Sanger sequencing of a second region of the viral genome. This approach was put in place to help address some of the challenges that exist when detecting and characterizing non-cultivable enteric pathogens. Details on this update to the assignment may be found in “Appendix A: Analytical Methods and Procedures.”



1. Firms whose product is being tested for pathogens by the FDA typically place the associated lots on a hold status, pending receipt of test results. The circumstances surrounding the agency’s decision to stop collecting samples at retail are detailed in the Sample Collection section of this report.

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