Galway's "boil water" alert is expected to continue indefinitely for 70,000 city dwellers, extending right through the annual film fleadh, arts festival and race week.
However, 20,000 people living in an arc extending from Tuam to Athenry, Claregalway and Oranmore should be able to resume drinking their tap water immediately, Galway's incident response team said yesterday.
Addressing a press briefing, the response team, involving the two local authorities and the Health Service Executive West was reluctant to give a definitive time scale for lifting the four-month-long alert in the city area.
The alert was put in place in mid-March in response to detection of unseasonally high levels of the cryptosporidium parasite, which causes gastrointestinal illness. Most laboratory confirmed cases of the illness involved the hominis version of the parasite, caused by human sewage. To date no one source has been identified.
Just under 50 people among 238 reported cases had to go to hospital, HSE West's public health director Dr Diarmuid O'Donovan confirmed yesterday. He estimated that up to five times the number of laboratory confirmed cases may have occurred in the Galway community.
Fewer than 10 cases, mainly affecting young children, became seriously ill and all had now recovered, Dr O'Donovan said.
Rod Killeen, senior engineer with Galway County Council, said that the "clock would start ticking" towards a clear supply when the old Terryland waterworks in the city was decommissioned. Under pressure from business interests, the local authorities had originally set June 15th as the target date. The city council then admitted in early June that there had been a "slide" in meeting the deadline.
"Complex engineering works" at the Luimnagh [ Tuam] waterworks plant involved installation of treatments to remove the cryptosporidium parasite which prompted the alert, Mr Killeen and his city counterpart, Ray Brennan, told yesterday's briefing.
They said that clear criteria had been set out by the HSE and the Environmental Protection Agency to lift the boil water notice, and Luimnagh's upgraded plant now had clean water, safe for human consumption.
The HSE West has said that no additional cases of cryptosporidiosis have been confirmed by laboratories in recent weeks, and occurrence of the potentially serious illness is now approaching "background levels" for this time of year.
HSE West is advising people with impaired immune systems to continue to follow their doctors' advice on boiling water.