Dr John Brooks, consultant microbiologist and director of Microtech Services, says the disease must have been in the berries through human waste – either through a handler, irrigation or contaminated water used in processing.
Nelson based FSL Foods was last week voluntarily recalling several berry product lines after four cases of Hepatitis A were linked to packaged imported frozen berries. MPI was not ruling out further recalls.
This follows an illness which was linked to pre-packaged berries. There was concern in New Zealand last year when a Hawke's Bay fruit packhouse worker was diagnosed with Hepatitis A.
Brooks says Hepatitis A does not colonise plants and fruits and cannot multiply on them.
"The contamination has most likely come from an infected food handler, but might have come from human waste used for field irrigation or from faecally contaminated water used in processing.
"There is nothing peculiar about berries; any food may be contaminated if infected handlers are careless about personal hygiene. A person known to be suffering from Hepatitis A should not be permitted to handle foods for others."
Dr Gail Greening, science leader/consultant, Environmental and Food Virology Laboratory, ESR, says the Hepatitis A virus shows high resistance to drying, heat, refrigeration, low pH, disinfectants and solvents and even survives in seawater for three months.
Pre-harvest contamination of fruits and vegetables, including strawberries, raspberries, blueberries, lettuce, semi-dried tomatoes and green onions, has been reported and has resulted in outbreaks of disease in Finland, the Netherlands, the US and Australia where populations have low or no immunity to the disease.
MPI's director plants food and environment Peter Thomson thanked FSL Foods for their cooperation in the recall. Any named recalled products at home should be discarded, he says.
"In the meantime, our advice about all other imported frozen berries stays the same. People should wash their hands before eating and preparing food. Anyone who is concerned should briefly boil any imported frozen berries before eating them, or ensure cooking exceeds 85°C for one minute.
