Galway city and county councils have confirmed serious contamination of public water supplies by a resistant parasite which can cause gastro-intestinal illness.
Evidence of the cryptosporidium organism in the Terryland city waterworks and at Headford, Co Galway, represents the largest single incidence and most extensive geographical spread of the contamination in the State since the associated illness became notifiable.
The two local authorities and the Health Service Executive (HSE) West confirmed this at a press conference in Galway yesterday evening, when representatives said it was "essential" that people in the affected areas continue to boil water intended for drinking or food preparation.
To date there have been some 60 cases of cryptosporidiosis, a diarrheal illness, reported in the Galway area since January - compared to 73 for all of Galway, Mayo and Roscommon last year.
Of these 60 cases, 36 occurred in the past three weeks, and four people have been treated in hospital.
Up to two of these cases were "serious", Dr Diarmuid O'Donovan, director of HSE West's public health department, confirmed last night. There is no cure for the illness, which causes diarrhoea, stomach cramps, upset stomach and a mild fever, and can last for two weeks. However, the parasite may continue in a person's system for up to two months.
Most people with a healthy immune system will recover, but people with weakened immune systems, such as the elderly, babies, people with HIV/Aids and people being treated for conditions such as cancer are at greater risk of more severe illness, HSE West says.
The "boil water" notice is expected to last for "weeks", affecting some 90,000 people in the city and surrounding county areas from Tuam in the north, to Athenry in the south and Moycullen in the west. Lough Corrib is suspected as the main source of the parasite, but HSE West is investigating other possible causes, Dr O'Donovan said last night.
Both the city and county councils say they are examining "all measures that can be put in place to ensure the quality of the water supply and to protect the integrity of the water sources".
Short term measures include increasing the current intake of water by the city from Tuam's regional supply from half-a-million gallons a day to two million gallons a day, and the installation of a "water treatment package", Ciarán Hayes, Galway City Council director of services said.
Long term measures would include installing a "major new water treatment plant" in Galway city, but this would "take time", Mr Hayes added.
Asked if a freeze should be put on all new housing developments until such time as there was an adequate water system, Mr Hayes said that this was a matter for another forum.
A team of 10 environmental health officers (EHOs) visited some 1,000 hotels, restaurants and other food providers over the weekend, and are continuing to work with nursing homes, creches, swimming pools and other facilities, Maurice Mulcahy, EHO and principal officer with HSE West said.
There was "no evidence" of secondary infections, as in person to person contact, as yet, Mr Mulcahy said.
Fianna Fáil Councillor Mike Crowe questioned whether the boil water alert should have been issued earlier, but urged people to pay serious attention to all precautionary measures.
A joint local authority meeting on the issue should be convened as soon as possible, he said.