Hunter emergency departments are experiencing "significant demands", amid a rise in illnesses in the colder weather.
"We have this demand now and we're expecting to see influenza activity increase over the next few weeks," public health physician Peter Murray said.
"That's what's got us worried."
Dr Murray, of Hunter New England Health, said "influenza is at moderate levels now but increasing".
The NSW Respiratory Surveillance Report, released on Thursday, showed 193 positive tests for influenza, 190 for RSV and 75 for COVID in Hunter New England. These results apply to people sick enough to be tested.
This time last year these numbers were 712 (influenza), 147 (RSV) and 201 (COVID).
Dr Murray said it had been "an unusual influenza season".
"We had that summer wave of influenza with the H3N2 subclade K, known as the super-K flu," he said.
"That's pushed back our influenza season a bit. It hasn't peaked like it did last year in winter.
"We had the circuit breaker of school holidays, when we often see respiratory activity drop, particularly influenza activity."
The surveillance report said "unplanned emergency department (ED) presentations for influenza-like illness" were rising.
Dr Murray said it remained "a good time for people to get their influenza vaccine, particularly those at high risk of severe illness".
The report said RSV cases had fallen from a high to moderate level, while COVID remained at a low level.
"We haven't seen much COVID through this winter so far," Dr Murray said.
"But there are lots of other respiratory viruses circulating at the moment, such as adenovirus and rhinovirus."
The Minns government this week urged people to keep away from emergency departments, unless they were severely ill.
NSW Health Minister Ryan Park said on Tuesday "if you don't have a life-threatening condition, please call Healthdirect".
Mr Park said the service provided "free health advice and you could potentially avoid an unnecessary wait in an ED".
"We also encourage people to stay up to date with their vaccines."
Premier Chris Minns said he had spoken to emergency departments in Maitland and Cessnock, "who have said it's a late starting season, but it's hitting us hard now".
Mr Minns urged people to go to an urgent care clinic or see a GP, so ED doctors and nurses "can focus their efforts and attention on people that are about to die".
Australian Medical Association (AMA) NSW president Fred Betros questioned the premier and health minister for urging people to avoid emergency departments.
"This is not an unforeseen crisis. It is a failure to prepare for predictable demand. The warning signs were impossible to miss," Dr Betros said.
"We need courage from politicians to invest beyond the election cycle."
NSW Health secretary Susan Pearce said a command centre had been set up to coordinate the management of peak hospital demand during winter.
"We've had command centres before in periods of peak demand, but now we're making it permanent," Ms Pearce said.
Healthdirect is on 1800 022 222 for 24-hour advice.
