Scientific tests are to be conducted by Health Service Executive West and Galway city and county councils during the weekend as part of the continuing alert over the drinking water supply.
Up to 90,000 residents in Galway city and large parts of the county are being advised to boil all drinking water as a public health measure during the alert. Hotels and restaurants have been visited by environmental health officers as shops and supermarkets reported a "run" on sales of bottled water.
Galway businesses were seeking alternative sources of bottled water and ice as they prepared for the busy holiday weekend, which marks the start of the tourist season.
The measures are "precautionary" and are aimed at reducing new diarrhoeal infections caused by ingesting the cryptosporidium parasite, according to the executive and the two local authorities. Testing has so far failed to confirm the presence of the parasite in drinking water supplies, but it is understood that the organism is difficult to detect.
Reported cases in the last 10 days suggested a pattern, initially clustered in the eastern and northern localities of Oranmore, Athenry and Tuam. The Tuam regional water supply has modern filtration equipment but is said to be overstretched due to population growth in the area.
Galway city's water supply is drawn almost exclusively from the Corrib and is filtered at the Terryland waterworks. However, the city also draws about half a million gallons of water daily from Tuam through the Lymnagh waterworks, and it exports some of the city supply to Barna and Moycullen.
Ciarán Hayes, Galway City Council director of services, denied yesterday the Terryland treatment plan did not have effective filtration systems and said the sampling there met all requirements set by the Environmental Protection Agency. Samples analysed yesterday from a number of locations were "clear", Mr Hayes said but monitoring will continue.
The executive advises that water should be boiled for drinking, for washing teeth, making ice and for preparing salads and other foods which are not cooked before eating. Domestic water filters will not render water safe to drink, it emphasises. When preparing baby feeds, bottled water is no substitute, as most brands contain excessive concentrations of minerals for babies.
The executive says that there is no drug to cure the infection, although some drugs may reduce the symptoms. It advises infected people to drink plenty of fluids to prevent dehydration.
Areas listed in the alert include all of Galway city and the areas of Athenry, Barna, Carnmore, Claregalway, Corofin, Headford, Lackagh, Oranmore, Tuam and Turloughmore. Some 80 group water supplies are also included. The lists and a detailed map are available online at www.galwaycity.ie as well as at www.galwaycoco.ie.
A similar alert involving the same parasite in drinking water occurred in the midlands and in Ennis, Co Clare, last year.