It has emerged that the city and county water supply in Galway has been contaminated by both human and animal waste.
Tests carried out in laboratories in Wales have also established that the strain of cryptosporidium parasite which has been found in water reservoirs and treatment plants can be transmitted from human to human.
The Health Service Executive says the situation remains a very serious one and it is of the utmost importance that all water is boiled before use.
Experts have told RTÉ News it could be up to six months before tap water is safe to drink in parts of Galway affected by pollution.
Up to 90,000 householders and businesses are affected, and today the number of cases of the cryptosporidium illness in the country rose to 125.
Business leaders in Galway city have demanded that the Government act to deal with the water pollution.
The local Chamber of Commerce and Industry said the problem was posing a threat to the tourist industry in the county.
The city council says work on finding a way of eliminating the cryptosporidium parasite, which is causing a widespread outbreak of gastro intestinal illness in the area, is still continuing.
Earlier today the council said it is likely to be up to two months before the current directive on boiling boil water can be lifted.
The news has drawn an angry reaction from local hoteliers and those involved in the catering and tourist industry.
They say there are now experiencing a worrying number of cancellations and the pollution scare is posing a serious threat to Easter holiday bookings.
Fianna Fáil Senator Margaret Cox has described the situation regarding as 'a national emergency'.
Fianna Fáil Senator Michael Kitt said he understands that the boiled water notice could be on display until next October, if there is not a resolution to the issue.