A growing number of people have been diagnosed with hepatitis A after eating frozen berries imported from China.
People have become ill after eating Nanna’s frozen mixed berries, prompting a national recall of the one-kilogram bags. Also recalled are the 300 gram and 500 gram packets of Creative Gourmet mixed berries, which were packaged in the same plant as the Nanna’s berries.
But how did the berries become contaminated in the first place? And why wasn’t the virus killed when the berries were frozen? We asked experts to explain how the contamination occurred.
How would berries have become contaminated with hepatitis A?
Associate Professor Sanjaya Senanayake, an infectious diseases expert from the Australian National University, said hepatitis A is transmitted by the “faecal-oral” route.
“This means that people who have contaminated hands can transmit the virus,” he said.
So the infection could have been spread by someone working at the plant, who was infected with hepatitis A and did not wash their hands properly before handling the berries.
“Or alternatively, because it’s excreted in the stool, whether there’s been a water supply that’s been contaminated with sewage, which contains hepatitis A virus, and that water has been involved in the processing. That’s another possible scenario,” he said.
Why didn’t freezing the berries kill the hepatitis A virus?
Professor Enzo Palombo, a food health and safety expert and chair of the Department of Chemistry and Biotechnology at Swinburne University of Technology, said freezing does not kill hepatitis A.
“While the virus does not grow in the frozen food, it still remains infectious and is essentially preserved during transport,” Professor Palombo said.
Then when the food starts to thaw, the virus again starts reproducing.
“It’s not just viruses, like hepatitis A, but the bacteria we associate with food-borne illnesses, like salmonella, e- coli, listeria, these all can survive freezing temperatures as well,” Associate Professor Senanayake said.
Does cooking kill the hepatitis A virus?
While cooking can kill the virus, the food needs to be thoroughly heated to above 75 degrees Celsius.
“If you heat food for a minute or two at that temperature, you should kill hepatitis A. But if you heat it to a lower temperature than that, then it’ll still survive,” Associate Professor Senanayake said.
He does not recommend cooking the berries that have been recalled, as these should be thrown out or returned to the place of purchase.
Is there anything consumers can do to avoid becoming ill when this type of contamination occurs?
While many people may be vowing never to eat frozen berries or similar products again, Associate Professor Senanayake said it was important to remember this was an unusual event.
“People who’ve been eating these berries for years haven’t been getting hepatitis A, because presumably the processing has prevented contamination of the end product,” he said.
“So I think that just because one product has become contaminated doesn’t mean that one should never have frozen berries again.
“A lot will depend on what went wrong, whether they can identify it and whether they can identify if it will ever happen again.”
Concerned consumers can call the company on 1800 650 069.