Visiting restrictions have been implemented at Portiuncula Hospital following an outbreak of the winter-vomiting bug.
Two wards at the Ballinasloe Hospital have been affected by the norovirus outbreak.
Visiting will now be restricted to a case by case basis on compassionate grounds, with visitors asked to contact the ward manager in advance.
Hospital management is urging anyone with symptoms such as diarrhoea or vomiting to avoid attending the hospital.
Anyone who has come in contact with someone with those symptoms are urged to clean their hands with alcohol gel or hot water and soap.
Visitors are also asked no to use patient toilets or en suites, and use the public toilets on the ground floor of the hospital.