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.”
Findings and Follow-up Actions
The FDA detected HAV in eight samples (1 strawberry, 5 raspberry, and 2 blackberry) and norovirus in 10 samples (3 strawberry, 3 raspberry, and 4 blackberry). These results made for HAV and norovirus prevalences of less than 1% for each of the three berry types.
The FDA compared the HAV and norovirus detection rates by origin (i.e., by their domestic-versusimport collection status) for each of the commodities. The agency did not find any statistically significant difference in contamination rates based on origin.
Whenever the agency detected HAV or norovirus under this assignment, the FDA oversaw the removal of all affected product from the U.S. distribution chain. All the domestic samples found to be violative resulted in a voluntary recall; all the import samples found to be violative were either refused entry into the United States, or they resulted in a voluntary recall of the affected lot. Additionally, in four cases, the FDA either flagged, for 180 days, all future shipments of the commodity by the responsible firm, such that all were subject to screening upon entry, or the FDA placed the firm and its product on Import Alert 99-35, which requires a firm to overcome the appearance of adulteration and be removed from the import alert before any entries can be released into domestic commerce.
The findings of this assignment, combined with the history of foodborne illness outbreaks linked to fresh and frozen berries, underscore the need for berry growers to comply with the FDA’s Produce Safety Rule, for frozen berry manufacturers and others in their distribution chain to comply with the FDA’s Preventive Controls for Human Food Rule, and for importers of these commodities to comply with the FDA’s Foreign Supplier Verification Programs Rule.
Strategy to Prevent Enteric Virus Outbreaks Associated with Fresh and Frozen Berries
In tandem with this assignment, the FDA has worked with industry experts and other interest holders to develop a prevention strategy for enteric viruses in fresh and frozen berries to help limit or prevent HAV and norovirus contamination and outbreaks associated with fresh or frozen berries. The prevention strategy was initiated in response to a history of HAV and norovirus outbreaks linked to the consumption of both fresh and frozen berries. It was not initiated as a result of the findings of this sampling assignment. The prevention strategy summary features goals and activities for the FDA, industry and other interest holders to prevent contamination of fresh and frozen berries with enteric viruses. Hygienic practices and challenges for the control of enteric viruses in berries and other hand-harvested produce apply globally. An approach that identifies, leverages, and shares effective practices can benefit domestic and global operators that grow, process, and source berries and other produce with similar risk factors.
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[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.