A long incubation period for hepatitis A of up to 50 days was "hampering the investigation" into a food poisoning outbreak of the virus linked to the consumption of imported frozen berries, according to Prof Alan Reilly, chief executive of the Food Safety Authority of Ireland.
The length of time for symptoms of the illness to show meant it was difficult to establish when the 10 patients infected with the virus had eaten infected berries, he added.
The virus which has broken out in Ireland is identical to an outbreak in Trento and Bolzano, in northern Italy. Fifteen people from Germany, Poland and the Netherlands were also infected but they had travelled to those areas of Italy for a skiing holiday.
Irish cases
Three Irish cases were first identified in April and since the beginning of July seven more cases have come to light including five on Wednesday evening.
The Food Safety Authority of Ireland, in addition to warning consumers yesterday to boil all frozen berries for a minute before consuming them, has also called on shops to check with their suppliers that frozen berry products are safe. “If reassurances of the safety of the frozen imported berries are not available, the berries should be cooked or boiled before being used in foods to eliminate or reduce the risk from foodborne viruses and pathogenic bacteria,” the authority said in an information note.
A warning to retailers was also issued at the end of June about checking with suppliers, Prof Reilly added.
'Cutting corners'
Alan Kelly, marketing manager with Zumo, which runs juice and smoothie bars in Ireland and 13 other countries, said the outbreak was probably linked to "someone somewhere cutting corners".
“It all comes down to how thorough the system is and how it is being regulated,” he said. “We have redoubled our efforts to ensure that our suppliers and everyone is compliant with standards. All batches at every production stage are tested for contamination.”
An outbreak of hepatitis A was also identified in Denmark, Sweden, Norway and Finland earlier this month. It involved 59 people infected, with possibly 103 further infections. The cases of infection in these countries were caused by a different hepatitis A, genotype 1B, compared with that causing infection in Ireland and Italy.
Another outbreak involving 39 travellers returning from Egypt to several European countries has also been identified but is also not linked to the Italian/Irish outbreak.