Oysters exported from Cork Harbour earlier this year have been blamed for an outbreak of the winter vomiting virus in Hong Kong.
The Food Safety Authority of Ireland (FSAI) traced the source of the outbreak after a complaint from the Hong Kong food safety authorities.
Mr Alan Riley, deputy chief executive officer of the FSAI, said the virus had been identified through a genetic fingerprint sample taken from the exported shellfish. Tests at a virus reference laboratory in the UK showed "without question, Irish oysters made those people in Hong Kong sick," he said.
It is thought the virus entered the food chain through sewage outfalls in the north channel of Cork Harbour. Live oysters from the area were exported in mid-January to Hong Kong where they were eaten raw.
The Department of Marine and Natural Resources closed the harbour for harvesting after the discovery. The Hong Kong authorities have since lifted a temporary ban on the importation of Irish oysters.
"Because we were able to demonstrate we could trace the source of this, no long-term damage has been done to our export business," said Mr Riley, adding: "luckily this is not a killer illness but it's very inconvenient."
The outbreak was discussed at a recent Irish Shellfish Association conference in Letterkenny, Co Donegal.
Mr Riley said it highlighted the need to ensure "robust monitoring controls" were in place to safeguard the €60 million a year shellfish industry. In this regard, he said, "Ireland badly needs a food virology reference laboratory so we can protect the health of people eating Irish foods both at home and abroad. At present, we are relying for this work to be done elsewhere."
He noted that live oysters were regarded as a "high-risk" food. Up to 90 per cent of food-borne viral illnesses are caused by live molluscs or shellfish.
As a result, he said, "we have excellent food safety controls in place. Within half an hour of getting the alert from Hong Kong we would have known where the oysters were coming from. It's a tragedy people got sick but it proves the controls are there, and work well."
The bug in question was identified as a "grade two norwalk-like virus".
Mr Riley said there was no question but it was the same virus which had affected hospitals throughout Ireland since Christmas.
Meanwhile, the Southern Health Board announced yesterday that the bug had spread to two new community hospitals in Dingle and Killarney.
Ten patients are in isolation at the hospitals with suspected small rounded structured virus (SRSV), according to the health board's consultant medical microbiologist, Dr Bartley Cryan.
The situation at Cork University Hospital has also worsened with 82 patients now being monitored in isolated wards. Tralee General Hospital has two patients in the same situation.
"We must emphasise that this highly contagious virus can be debilitating in older people and young children and in fact all persons who are already ill in hospitals and nursing homes.
"We are therefore appealing to the public to only visit these facilities if absolutely necessary, in an attempt to limit the spread of this disease," said Dr Cryan.
Elective surgery has been cancelled at the hospitals. Only next-of-kin of critically ill patients are advised to make visits.
Cork University Hospital has set up an information line at (021) 492 2112. The Southern Health Board's information line is 1850 742 000.