Montecillo Veterans Home and Hospital, in Dunedin, has closed its doors to visitors as staff try to contain a vomiting and diarrhoea outbreak.
Ten residents and four staff had been hit by the bug in the past few days, manager Fred Daniel said yesterday.
"We are unsure exactly what the bug is, but we decided it was best to put a ring fence around the place and restrict entry," he said.
Sick residents were being cared for in their rooms, he said.
No extra staff had been called in as staff had not been sick in large numbers.
Mr Daniel said he did not know how long visitors would be restricted - "once we are clear of any new cases for 48 hours, we will open up again."
A similar bug has hit other Dunedin rest-homes in the past three weeks.
Radius Fulton Home clinical manager Doug Browning said three residents had been affected three weeks ago, but no residents were ill at present.
One resident at Yvette Williams rest-home was ill last week, but prompt action from staff had stopped it from spreading, manager Jane Griffin said.
Two residents at Frances Hodgkins home had vomiting and diarrhoea this week, but there was no general outbreak, Ryman Healthcare chief executive Simon Challis said. Staff were on "red alert" to stop that happening, he said.
Southern District Health Board medical officer of health Dr Derek Bell said there were always bugs in the community and in rest-homes and the picture this week was "fairly typical for this time of year".
"We are aware of an increase in vomiting and diarrhoea cases in another Dunedin rest-home, and an increase in some cases of flu-like illnesses in the general population in Dunedin and rural areas."
No problems had been reported at Dunedin Hospital, he said.
