University College Hospital in Galway has cancelled elective surgery after an outbreak of the so-called Winter Vomiting Bug.
A spokeswoman for the hospital said "several suspected cases" had been reported and appealed to members of the public to cancel hospital visits, unless they were urgent.
"We are appealing to people to help stop the spread of this virus", she said, adding that those on essential visits should avoid moving between the hospital's wards.
The hospital, which has 550 beds, will continue to perform essential operations and its emergency departments will remain open.
Meanwhile the Western Health Board is continuing to advise parents to have their children immunised with the Measles, Mumps and Rubella (MMR) vaccine after an outbreak of measles in Tuam, Co Galway.
Twenty children at a day-care centre and a primary school have been diagnosed with the potentially life-threatening disease in the past two weeks.
A special clinic set up to administer the MMR yesterday was reported to be busy. The clinic will continue its work tomorrow when public health teams will visit primary schools in the area. It is believed an immunisation programme will be extended to other parts of Co Galway during the week. A helpline (1800-622211) will also open again tomorrow.
Continuing fears about the safety of the MMR vaccine have led to a recent drop-off in the number of parents having children immunised. But medical experts have repeated that there is no proven risk of autism or bowel disease stemming from the vaccine.
The health board is desperate to prevent an epidemic following the deaths of three children during a major outbreak in Dublin in 2000. More than 1,500 children also fell ill.
