Scientific testing has continued in Galway over the weekend to try to establish the source of a gastric illness which could be linked to drinking water.
The precautionary instruction to boil water is expected to remain in place for some days and medical experts and city and county officials are due to meet tomorrow to assess the situation.
No new cases of the diarrhoeal illness cryptosporidiosis were reported over the weekend, Dr Diarmuid O'Donovan, director of public health at Health Service Executive (HSE) West, said yesterday.
However, the 47 cases notified so far might just be the "tip", he said, as some people may not have sought medical help.
The 47 incidences have occurred in Galway city and county since January, 14 of them in the past week. A total of 73 cases were recorded in Galway, Mayo and Roscommon last year.
Testing has so far failed to confirm the presence of the cryptosporidium parasite in drinking water supplies, but the organism is difficult to detect.
Symptoms of cryptosporidiosis include diarrhoea, stomach cramps, upset stomach and a mild fever and can last for two weeks.
The illness, which is linked to the lambing season and to contact with animals, was one of a series which became notifiable under law in January 2004. Since then, similar alerts have occurred with water supplies in the midlands and in Ennis, Co Clare.
The infection is spread by swallowing anything which has come into contact with faeces or by swallowing contaminated water in a swimming pool, a jacuzzi, a lake, a river or a pond. It can also be contracted through eating uncooked contaminated foods.
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.
Environmental health officers were on duty in Galway city and county over the weekend and were visiting restaurants, hotels and pubs to give advice on the preparation of food and drink. An information telephone line has been set up for hospitals, nursing homes and hotels and food and drink outlets.
The Mayor of Galway, Niall Ó Brolcháin (Green Party), has tabled an emergency motion before Galway City Council calling on it to install treatment measures which prevent the parasite from entering the water supply. The council maintains that its filtration systems are adequate.