According to the story, hospital managers say it also led to some delays in admissions amid reports of hold-ups in the accident and emergency department.
Admissions to the two wards have been suspended until patients' symptoms have gone.
About nine patients are suffering from the bug whose symptoms include diarrhoea or vomiting.
The Betsi Cadwaladr health board which manages the hospital advised anyone with the symptoms not to visit for 48 hours to avoid passing on the bug more commonly seen during the winter.
Llyr Gruffydd, AM for North Wales, said: “These are problems entirely of Betsi Cadwaladr’s own making because it recently closed four community hospitals and lost 50 beds. The chickens are coming home to roost.
"Back in March, when Llangollen and Flint hospitals were closed, we warned that a lack of spare capacity and losing community facilities without adequately replacing them would create bed-blocking problems in district general hospitals such as Wrexham Maelor.
“The Health Minister has sent in a new team to sort out senior management in North Wales but there’s little sign that the sort of changes needed to improve our health service are taking place. Reducing bed blocking so that ambulances aren’t being used to treat A & E patients should be an immediate priority. ”
Mabon ap Gwynfor, of the North Wales Health Alliance, said : “If hospital occupancy rates go above 82% it’s recognised that hospital-acquired infections including norovirus are far more likely to occur.
"Health experts understand this so it’s surprising that Betsi Cadwaladr has not considered this in their recent review, which centralised services and has seen occupancy rates in our general hospitals of 87%.
“Rushing the closure of community hospitals without planning for their replacements is putting more pressure on clinical staff. Managers have got it wrong and need to rethink their plans.”