Smoothie fans, take note: The FDA now tests frozen berries for hepatitis A, norovirus

The Food and Drug Administration is being cautious about frozen, edible, colorful fruits.

The FDA has begun testing frozen berries for hepatitis A and norovirus. The sampling, which started in November and is expected to last for 18 months, was prompted by four frozen-berry-related outbreaks in U.S. between 1997 and 2016.

The concern is that people don’t always cook the frozen strawberries, raspberries and blackberries before using them – think smoothies versus blueberry muffins. The issue is that cooking would reduce or eliminate the contamination. 

The FDA has given no specific guidance about how to prepare frozen berries meanwhile.

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Experts say the hepatitis A and norovirus could come from ill farm workers or contaminated irrigation water or surfaces, like a harvesting basket.

The three hepatitis A outbreaks in the U.S. caused 405 people to get sick and 53 were hospitalized, while the one norovirus outbreak made 136 people ill, according to the FDA.

Frozen-berry virus outbreaks have been a bigger problem in Europe than in the U.S., but this country needs to take action, too, according to Don Schaffner, a professor of food science at Rutgers University. His lab's recent research found that viruses can survive for two years frozen.

"Just because there have not been outbreaks, you could still have problems under the radar," he said. "Washing is not going to be 100% (effective). What you really need is good agricultural practices on farms to make sure sick workers are not working on farms and high-quality water is used."

The FDA said it plans to collect a total of 2,000 samples – domestic ones from processors, distribution centers, warehouses and stores and imported ones from ports of entry, importer warehouses and other storage facilities. The FDA said it will post its findings quarterly.

Follow USA TODAY reporter Zlati Meyer on Twitter: @ZlatiMeyer