A scientific report for the Department of Health on risks posed by the waterborne cryptosporidiosis parasite advised that a national expert group should be established to deal with contamination cases.
A national reference laboratory to "type" the parasite could also help to identify the source of infection, the report by a sub-committee of the scientific advisory committee of the National Disease Surveillance Centre (now the Health Protection Surveillance Committee) advised.
The report, which drew up a series of recommendations for the Department of Health in November 2004, noted that monitoring of cryptosporidium had been most extensive in Dublin, Kildare and Wicklow in a five-year period to 2000.
One of its principal recommendations was that local liaison groups involving public health and local authorities should be established before incidents of contamination occurred.
While acknowledging that the parasite - which has now infected Galway city and part of county supplies in the State's largest outbreak - is very hard to detect, it noted that prevention could be achieved with proper risk assessment and follow-up action.
Environmental Protection Agency (EPA) data from local authorities has already shown that one in five public water systems faces a cryptosporidium contamination risk. The water supply for Galway city was among 13 per cent of public supplies identified as at "very high risk" two years ago.
The report noted that cryptosporidiosis, caused by the parasite, has been associated with many large-scale outbreaks of serious disease worldwide. The largest outbreak in public water supplies claiming over 100 lives when over 400,000 people became ill in Milwaukee, USA, in 1993.
The report cites data from two Irish studies on paediatric populations which showed that approximately 4 per cent of acute diarrhoea in children is caused by cryptosporidiosis.
Data from three of eight health board authorities also showed an average of 121 cases per annum among a population of 1.2 million people.
The number of cases in Galway city and county is now running at 125 with at least six of those reported to be in hospital.
However, the mayor of Galway, Niall Ó Brolcháin (Green Party), said yesterday that he believed there were "hundreds" of people affected.
The incident response team involving the Health Service Executive (HSE) West and the two local authorities also said that initial results on the small number of human specimens tested so far have detected the presence of cryptosporidium hominis (the type that can be transmitted from human to human), along with cryptosporidium parvum (animals to humans).
"This testing will continue in an effort to get a better understanding of the outbreak," it said.
The local authorities are continuing to carry out sampling of water supplies and to identify the source of the contamination.
The NDSC report of 2004 noted that agricultural pollution was one of three possible sources, with severe overloading of or bypassing of filters in water treatment works being a second.
It also said that it could occur following exceptionally heavy rainfall after a dry spell, especially after recent slurry spreading.
Galway Chamber of Commerce has expressed concern about the impact on tourism of the continued "boil water" notice, which may last months, and says some hoteliers are reporting a 20 per cent drop in bookings.
The notice does not affect Connemara, with western limits to date being at Moycullen.
Minister for Community, Rural and Gaeltacht Affairs Eamon Ó Cuív claimed that €21.5 million had been allocated in 2002 by the Government to upgrade Galway city's outdated waterworks. However, Galway City Council said it had been working continuously with the Department of the Environment on the project and had "advanced proposals as far as we can at this point".