Restrictions were put in place earlier this week that limited the number of visitors to the 28-bed veterans unit at Harbourview Hospital in Sydney Mines.
But the Cape Breton District Health Authority says it is no longer permitting any visitors, including immediate family and next of kin, until further notice.
It says exceptions may be made for compassionate reasons.
The authority says nine of the unit's 28 patients were experiencing gastrointestinal symptoms as of Friday.
The illness can cause nausea, vomiting, diarrhea and cramps and is spread easily by close contact between people.