With 1204 people hospitalised with the virus on Monday - up from 1066 the day before - and more than 2500 health workers furloughed, the health system is under strain.
"We are seeing health systems around the world put under stress and whilst we are very well placed ... it is important that we all play our part in not placing unnecessary burden on the health system," Chief Health Officer Kerry Chant said on Monday.
People should avoid going to the emergency department to seek PCR tests for COVID-19 if they're not unwell, Dr Chant said.
"That potentially compromises the care of those that need it," she said.
"I know that people want to know what their diagnosis is ... but can you also just think about some of the implications of those actions."
Dr Chant reassured NSW residents that the health system is available for those who need it, urging people with health concerns not to delay seeking treatment.
As of December 30, 2510 healthcare workers were in isolation after being exposed to COVID-19.
Intensive care numbers jumped by 12 to 95 overnight. Twenty-five people are ventilated.
Not all those in hospital with coronavirus were admitted for treatment for COVID-19, according to new data.
NSW Health says that a small sampling of hospital patients with COVID-19 in two local health districts over the past two weeks shows that some were admitted for unrelated illness or injury.
They include women giving birth, people seeking mental health care, and people with appendicitis or bowel obstruction, a NSW Health spokesperson said in a statement.
The agency did not respond to questions about whether a similar proportion of hospitalisations during the Delta wave was primarily for other reasons.
The spokesperson said it's to be expected that some patients will present with other conditions as their primary reason for seeking health care, as case numbers rise.
Opposition Leader Chris Minns said it was "not immaterial" that there was a rising number of admissions throughout the hospital system.
A high rate of COVID-19 among hospital patients still means extra measures must be taken by frontline workers to keep themselves and others safe, even if patients were admitted for other reasons, he said on Monday.
Dr Chant also urged parents to get their children vaccinated before school returns in four weeks.
The vaccination rate for children aged 12 to 15 had been "stubborn", lingering around 80 per cent, she said.
"We would like to see children fully vaccinated to commence the school year and because of the interval you need to act now so they can get the two doses in before commencing school," she said.
The latest figures show 95 per cent of NSW residents aged 16 and over have had one dose of the vaccine and 93.6 per cent have had two doses.
Some 81.5 per cent of 12 to 15-year-olds have been vaccinated once, and 78.2 per cent twice.
The new cases were diagnosed from 96,765 tests processed in the 24 hours to 8pm on Sunday.
The four deaths included two people in their 70s and one each in their 80s and 90s.
Cases are surging in western Sydney, which had 4047 new cases, closely followed by south western Sydney with 3966 cases.
Twelve new cases were diagnosed in the state's jails.
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