On this page:
- Frozen Berries Surveillance Sampling
- Questions and Answers
- Results as of 7/1/2023
- Additional Information
Frozen Berries Surveillance Sampling
Frozen berries are used as ingredients in many foods and, like other produce, can be an important part of a healthy eating pattern. While frozen berries are used in pies and other baked goods, they are also used raw in fruit salads or smoothies and have been associated with outbreaks of foodborne illness. The FDA reported three hepatitis A virus outbreaks and one norovirus outbreak linked to frozen berries in the United States from 1997 to 2016.
Strawberries, raspberries, and blackberries are delicate and may become contaminated with bacteria or viruses if handled by an infected worker who does not use appropriate hand hygiene, or if exposed to contaminated agricultural water or a contaminated surface, like a harvesting tote. In general, berries typically are not washed after harvest or prior to distribution because post-harvest exposure to water can accelerate spoilage and shorten the commercial shelf life of most berries. Freezing preserves berries but generally does not kill viruses, which can survive at low temperatures.
The FDA is collecting samples Monday to Friday, during business hours.
The FDA is collecting domestic samples of frozen berries from processors, distribution centers, and warehouses. The FDA initially collected some samples at retail locations but has since removed retail (i.e., grocery) collection from the sampling assignment to minimize the amount of product in commerce in the event of a positive sample, thereby further strengthening public health while minimizing market disruption. The agency is collecting import samples of frozen berries from ports of entry, importer warehouses, and/or other storage facilities where foreign goods are cleared for entry into the country.
Samples may be collected from the same establishment or importer on more than one occasion. To minimize impact on any one firm, the FDA will not exceed three collections every six months from the same establishment, as a general rule, assuming no violations are found.
The FDA initially planned to collect and test a total of 2,000 samples of frozen strawberries, frozen raspberries, and frozen blackberries in retail packaging (1,000 domestic, and 1,000 of international origin) for purposes of this assignment. After pausing the assignment in connection with the COVID-19 pandemic, the FDA has reduced its collection target to approximately 1,547 samples, which will facilitate completion of the assignment while also meeting the agency’s public health goals. The FDA has met its collection target for frozen strawberries and so is no longer collecting that type of frozen berry.
The FDA is testing samples for hepatitis A virus and norovirus. From the beginning of the assignment the FDA used an RT-qPCR method that has undergone multi-laboratory validation by the FDA for the detection of hepatitis A virus and norovirus in soft fruit. While this remains the primary test for this assignment, starting in August 2019, we also initiated Sanger sequencing as a routine component of the assignment in order to further characterize viral sequences present in any RT-qPCR positive samples.
We will be pre-announcing visits to collection sites in light of the COVID-19 pandemic to help assure the safety of industry employees and FDA investigators, and to improve the efficiency of sample collection. Additionally, FDA field staff will be equipped with personal protective equipment (PPE) and will adhere to local, state, and applicable CDC guidance to help protect their health and the health of firm employees.
If the FDA detects hepatitis A virus or norovirus RNA in a sample, the agency will notify the firm of the findings and work with the firm to take appropriate action to protect the public health. Enforcement activities include actions to correct and prevent violations and to remove violative food from the market, as appropriate. Since July 2019, the FDA began notifying firms of RT-qPCR positive samples and the results of the Sanger sequencing to further characterize the samples before asking the affected firms to conduct a voluntary recall of the product.
See detailed information on what to expect when the FDA collects samples
The FDA plans to publish the final test results once the assignment and related analysis are complete. We anticipate this being our final interim update. Sample collection will be completed no later than September 30, 2023, with a final report expected in 2024.
The FDA is sensitive to the concerns of domestic firms and importers and strives to provide analytical results to industry as soon as they are available. The FDA will notify firms of all analytical results as soon as possible once sample analysis is complete.
The information that follows presents the laboratory results as of July 1, 2023 as interim figures subject to potential revision. The FDA may adjust the number of samples to be collected or the collection timeline based on factors that the agency may encounter during the assignment.
The FDA will publish a summary report of its results (to include final figures and breakdowns of its findings) once the assignment is complete. People who wish to see an example report on the FDA’s food product surveillance sampling can view any of the agency’s summary reports listed at the bottom of its microbiological surveillance sampling page.
In the event that samples are found to be positive for microbial hazards, the FDA will consider regulatory and enforcement options. Enforcement activities include actions to correct and prevent violations, and to remove violative food from the market. The agency will detail any enforcement action it takes in its summary report.
The agency plans to collect and test 1,547 samples of frozen berries under this assignment. As of July 1, 2023, the agency had collected and tested 527 domestic samples and 995 import samples (1,522, or 98 percent of the total). The following figures summarize the interim sampling results. As the testing is still underway, no conclusions can be drawn at this time.
* 1 Blackberry, 1 Raspberry, 1 Strawberry
** 1 Blackberry, 2 Raspberry, 1 Strawberry. In addition to the four RT-qPCR positives designated as “Lab Class 3,” the FDA detected norovirus in two samples of frozen raspberries (also based on RT-qPCR testing) but did not conduct Sanger sequencing of these two particular specimens. In the case of one of the two specimens, the FDA suspended testing and further sample collections in response to the COVID-19 pandemic. In the case of the other, which was collected shortly after sampling began, a revision to the assignment to discontinue sampling at retail rendered the specimen inconsistent with the updated collection criteria and related testing scheme.
‡ In addition to testing the samples using pathogen specific RT-qPCR assays, the FDA is characterizing the RT-qPCR positives with Sanger sequencing. Of the seven positive RT-qPCR results, five were further characterized by sequencing of separate, non-contiguous sections of the viral genome. The agency will further describe the characterization results in its summary report.
* 2 Blackberry, 4 Raspberry
† 3 Blackberry, 2 Raspberry, 2 Strawberry
‡ In addition to testing the samples using pathogen specific RT-qPCR assays, the FDA is characterizing the RT-qPCR positives with Sanger sequencing. Of the thirteen positive RT-qPCR results, nine were further characterized by sequencing of separate, non-contiguous sections of the viral genome. The agency will further describe the characterization results in its summary report.