Unwell residents are asked to stay in their rooms and sick staff are sent home until they have recovered.
"It would be best if people did not visit friends or family at these three rest homes until the outbreaks are over," he said.
Nurses who managed outbreaks last year say that there appears to be a difference in the severity of illness from this year's Sydney strain.
A norovirus outbreak last year affected 288 people in six Northland rest homes and was linked to the deaths of two elderly residents. The affected rest homes are restricting access to visitors until the outbreaks are contained.
Dr Jarman said norovirus is a really infectious bug and one of the best ways to prevent spread is thoroughly washing and drying your hands.
People should see a doctor if vomiting is severe, the illness does not get better after 1-2 days, or if they are worried.