The mode of operation, usually reserved for external emergencies such as natural disasters, will come into effect tomorrow at midday at all metropolitan hospitals and six regional hospitals including AWH.

AWH acting chief executive Lucie Shanahan said the code brown was justified, but said their service wasn't yet recalling staff from planned leave - which the code brown designation allows them to do.

"Whilst we have seen increasing numbers of people requiring admission into the hospital in the last couple of days in particular, we are still working through some other strategies that we have to be able to deploy staff," she said.

"There were 10 people admitted this morning and a couple should be discharged, but we do expect ... sustained demand for at least the next couple of weeks locally.

"Certainly recalling people from leave would be one of our last alternatives.

"We do know that there is an increasing level of fatigue across our staff group, as there is for every health service."

Ms Shanahan said no one was currently in ICU but a spike in hospitalisations was expected over coming weeks.

"Given that we saw high new diagnosis rates in our community seven to 10 days ago, we are now moving into the phase where people's illness has progressed and we are seeing a fairly steady number of people presenting to the emergency department," she said.

Acting Health Minister James Merlino said the healthcare system was under "extreme pressure" with around 4000 staff unavailable.

While AWH has not disclosed the number of staff off work, changes were being made last week due to impacts.

Non-urgent community mental health services including Benambra Rehabilitation Service were "scaled back" to ensure continuous provision of 24/7 emergency care.

Ms Shanahan said the code brown gave AWH the option to scale back other services, if needed.

"This will place us in a position very similar to where we were in about October, November last year when we did enact our own code brown locally," she said.

"It means that we are in a position where if we need to, we can turn off particular services or stop delivering particular services to be able to deploy staff ... into critical areas.

"We're not yet at a point where we need to undertake wide-scale reduction in services across Albury Wodonga Health, but this is a really great opportunity for us to make sure that we are well-planned.

"We were looking very closely at whether we needed to enact emergency response plans for a number of services anyway ... we're in a position now where we can enact those as part of their statewide coordination ... as we need."

The declaration has been made according to levels of operation; Northeast Health Wangaratta is not part of the code brown and neither are smaller health services.

However, the Victorian government flagged "an expansion of COVID streaming sites to increase the number of hospitals caring for coronavirus patients" which could see greater responsibilities for smaller services.

The Pandemic Code Brown is expected to last four to six weeks.

Ms Shanahan said the community responded "exceptionally well" to her call-out last week for people to only present to the emergency department for emergency care.

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"As the Department of Health in Victoria does call the code brown response, it is a timely reminder for the community to ensure that if if you are coming to hospital or accessing an emergency department it is for emergency care needs," she said.

"The possibility of a code brown was something that certainly had been discussed and was being considered - we weren't surprised."