The Northumbria Healthcare NHS Foundation trust has been battling cases of the winter vomiting bug at its sites for around three weeks.
On December 29 the number of ward closures had dropped to one after reaching as high as 10 in the run-up to Christmas.
But on Thursday, January 4, the trust confirmed that the number of sealed wards had gone back up to six - including one at Blyth Community Hospital, which had been previously unaffected.
Trust bosses introduced visitor restrictions at nine hospitals across North Tyneside and Northumberland in a bid to stop the bug spreading further.
On Thursday visitor restrictions will be lifted for one hour between 2pm and 3pm, on wards that have not been affected by norovirus and limited to two visitors per bed.
A spokesperson said: “This isn’t just one large outbreak – as both flu and norovirus are in the community it will continue to be brought into our hospitals.
“Often this is unavoidable – if the patient is frail or very young for instance – as anyone in need of care will always receive it.
“However, wherever possible we are urging residents to either call 111 or talk to a pharmacist rather than risk bringing either bug into the hospital. Both are nasty but with common sense steps – drinking lots of water and staying warm – they can be managed.”
The trust is also strongly recommending that no children under the age of 16 come to any hospital site as a visitor to inpatient wards and facilities due to the on-going flu and norovirus outbreaks.
A spokesperson said: “They will not be allowed to visit maternity, pregnancy assessment or the birthing unit under any circumstances. Only immediate family will be permitted to visit the Special Care Baby Unit.
“This is for both their own and our patient’s safety as they are among the most at risk of catching and/ or carrying both flu and norovirus.”
They added: “In areas where visiting is open please remain vigilant: wash your hands thoroughly (soap and water – not alcohol gel).
“Please do not visit if you have symptoms of norovirus or any respiratory or flu-like symptoms; you will only endanger yourself, our staff and your loved ones.
It is expected that visitor restrictions will be partially lifted for unaffected ward on Friday.
Northumbria Healthcare revealed that the initial outbreak, which was confirmed on December 18, is believed to have started when a visitor brought mussels onto a ward for a patient at Wansbeck General Hospital.