Frozen berries carry major risk of hepatitis A contamination

Over the past year, food recalls have become a major concern, with frozen berries receiving increased scrutiny due to their vulnerability to contamination by enteric viruses like hepatitis A and norovirus. A Dutch supermarket was forced to conduct a massive recall due to hepatitis A infections linked to contaminated frozen blueberries. In response to this alarming trend, the US Food and Drug Administration (FDA) has implemented a “prevention strategy” aimed at improving the safety of fresh and frozen berries for consumers. 

Enteric viruses, which infect the intestines and cause symptoms such as diarrhea, nausea, and stomach pain, have been linked to outbreaks involving imported berries. According to an article on the Prevention website, frozen berries contaminated with hepatitis A and norovirus have been identified as a significant public health concern worldwide. According to the In 2024, a joint United Nations and World Health Organization panel classified these contaminated products as one of the highest global public health burdens. 

In the Netherlands, for example, contaminated frozen blueberries from one of the country's largest retailers Albert Heijn were linked to a hepatitis A outbreak, infecting at least 12 people in November 2024, with two even requiring hospitalization. The Dutch public health institute RIVM confirmed that it fears several hundred people could have already become infected with the hepatitis A virus as a result of the contamination. 

US outbreaks of hepatitis A outbreaks in 2022 and 2023 were traced to organic strawberries from a grower in Baja Mexico, resulting in 10 illnesses and four hospitalizations across multiple states. The FDA’s prevention strategy emphasizes sanitation throughout the berry production process, including harvesting, processing, and storage. 

One significant challenge in ensuring the safety of berries lies in their delicate structure, which often necessitates hand-harvesting. According to food safety expert Benjamin Chapman, Ph.D., from North Carolina State University, sick harvesters or those with poor hygiene practices can transfer viruses directly to the berries. This issue has been identified as a root cause in numerous contamination incidents. Once contaminated, berries are difficult to sanitize without damaging them.

However standard washing processes are not feasible, as they can reduce berries to pulp, and freezing does not neutralize viruses; in fact, viruses can survive freezing and remain infectious.

The FDA key measures include ensuring proper hygiene among field workers, maintaining sanitary facilities, preventing cross-contamination during harvesting and processing, and monitoring farm and facility workers for potential viral exposure. These steps aim to address the high risks posed by the delicate nature of berries, which makes them prone to contamination.

How you can protect yourself

To further address these challenges, research suggests that sanitizing berries with a mix of water and sanitizers like peroxyacetic acid and hydrogen peroxide can help reduce viral contamination. Infectious disease expert Amesh Adalja, M.D., from Johns Hopkins, emphasizes that while the individual risk from consuming berries is low, outbreaks linked to contaminated products highlight the importance of proper hygiene and preventive measures. Consumers are advised to wash berries thoroughly, even if labeled as “pre-washed,” to minimize potential risks.

In summary, the FDA’s updated strategy seeks to address the vulnerabilities of berries to enteric viruses through enhanced sanitation practices at every stage of production. These measures aim to protect consumers while responding to the global public health concerns posed by contaminated fresh and frozen berries.

By Nazrin Sadigova