Ward 14 at Dumfries Infirmary has been closed to new admissions due to an outbreak of norovirus.
Staff say full outbreak control measures are being implemented and the ward is also closed to routine visiting.
Four patients and one member of staff have reported symptoms of diarrhoea and vomiting, clinically consistent with norovirus infection.
A spokeswoman said: “The hospital’s infection control team is closely monitoring the situation to ensure that all appropriate infection control procedures are in place.
“Staff are working hard to minimise the discomfort and distress for patients and to maintain services.”
Elaine Ross, Infection Control Manager, said: “We can confirm that norovirus is circulating in the community. We would urge anyone with suspected symptoms to stay at home, drink lots of fluid and follow basic hand hygiene advice.”
The advice to members of the public wishing to visit the closed wards is:
* Routine visiting to the closed wards is suspended meantime and members of the public seeking to visit relatives and friends in hospital are advised not to travel whilst the outbreak measures are ongoing - to avoid the potential for further spread.
* Where circumstances are such that relatives are concerned about the need to visit their loved ones in the affected wards they are asked to contact the ward concerned before coming to the hospital.
* All members of the public visiting other areas of the hospital are asked to comply with the hand hygiene and infection control measures in place.